True identity of mysterious gamma-ray source revealed

 An international research team including members from The University of Manchester has shown that a rapidly rotating neutron star is at the core of a celestial object now known as PSR J2039?5617

The international collaboration used novel data analysis methods and the enormous computing power of the citizen science project Einstein@Home to track down the neutron star's faint gamma-ray pulsations in data from NASA's Fermi Space Telescope. Their results show that the pulsar is in orbit with a stellar companion about a sixth of the mass of our Sun. The pulsar is slowly but surely evaporating this star. The team also found that the companion's orbit varies slightly and unpredictably over time. Using their search method, they expect to find more such systems with Einstein@Home in the future.

Searching for the so-called 'Spider' pulsar systems -- rapidly spinning neutron stars whose high-energy outflows are destroying their binary companion star, required 10 years of precise data. The pulsars have been given arachnid names of 'Black widows' or 'Redbacks', after species of spider where the females have been seen to kill the smaller males after mating.

New research published in, Monthly Notices of the Royal Astronomical Society, details how researchers found a neutron star rotating 377 times a second in an exotic binary system using data from NASA's Fermi Space Telescope.

The astronomer's findings were uniquely boosted by the Einstein@Home project, a network of thousands of civilian volunteers lending their home computing power to the efforts of the Fermi Telescope's work.

The group's search required combing very finely through the data in order not to miss any possible signals. The computing power required is enormous. The search would have taken 500 years to complete on a single computer core. By using a part of the Einstein@Home resources it was done in 2 months.

With the computing power donated by the Einstein@Home volunteers, the team discovered gamma-ray pulsations from the rapidly rotating neutron star. This gamma-ray pulsar, now known as J2039?5617, rotates about 377 times each second.

"It had been suspected for years that there is a pulsar, a rapidly rotating neutron star, at the heart of the source we now know as PSR J2039?5617," says Lars Nieder, a PhD student at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover. "But it was only possible to lift the veil and discover the gamma-ray pulsations with the computing power donated by tens of thousands of volunteers to Einstein@Home," he adds.

The celestial object has been known since 2014 as a source of X-rays, gamma rays, and light. All evidence obtained so far pointed at a rapidly rotating neutron star in orbit with a light-weight star being at the heart of the source. But clear proof was missing.

The first step to solving this riddle were new observations of the stellar companion with optical telescopes. They provided precise knowledge about the binary system without which a gamma-ray pulsar search (even with Einstein@Home's huge computing power) would be unfeasible.

The system's brightness varies during an orbital period depending on which side of the neutron star's companion is facing the Earth. "For J2039-5617, there are two main processes at work," explains Dr. Colin Clark from Jodrell Bank Centre for Astrophysics, lead author of the study. "The pulsar heats up one side of the light-weight companion, which appears brighter and more bluish. Additionally, the companion is distorted by the pulsar's gravitational pull causing the apparent size of the star to vary over the orbit. These observations allowed the team to get the most precise measurement possible of the binary star's 5.5-hour orbital period, as well as other properties of the system."

With this information and the precise sky position from Gaia data, the team used the aggregated computing power of the distributed volunteer computing project Einstein@Home for a new search of about 10 years of archival observations of NASA's Fermi Gamma-ray Space Telescope. Improving on earlier methods they had developed for this purpose, they enlisted the help of tens of thousands of volunteers to search Fermi data for periodic pulsations in the gamma-ray photons registered by the Large Area Telescope onboard the space telescope. The volunteers donated idle compute cycles on their computers' CPUs and GPUs to Einstein@Home.

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New discovery for how the brain 'tangles' in Alzheimer's Disease

 University of Queensland researchers have discovered a new 'seeding' process in brain cells that could be a cause of dementia and Alzheimer's disease.

UQ's Queensland Brain Institute dementia researcher Professor Jürgen Götz said the study revealed that tangled neurons, a hallmark sign of dementia, form in part by a cellular process that has gone astray and allows a toxic protein, tau, to leak into healthy brain cells.

"These leaks create a damaging seeding process that causes tau tangles and ultimately lead to memory loss and other impairments," Professor Götz said.

Professor Götz said until now researchers did not understand how tau seeds were able to escape after their uptake into healthy cells.

"In people with Alzheimer's disease, it seems the tiny sacs transporting messages within or outside the cells, called exosomes, trigger a reaction which punches holes in the wall of their own cell membrane and allows the toxic seeds to escape," he said.

"As more tau builds up in the brain, it eventually forms tangles, and together with abnormally configured proteins known as amyloid plaque, they form the key features of these neurological diseases."

Queensland Brain Institute researcher Dr Juan Polanco said the findings would help scientists piece together how non-inherited forms of Alzheimer's disease and other dementias occur.

"The more we understand the underlying mechanisms, the easier it will be to interfere with the process and to slow down or even halt the disease," Dr Polanco said.

"Along with Alzheimer's, this cellular process might also play a leading role in other cognitive diseases, from frontal lobe dementia to rare neurological disorders with toxic tau.

"Even in cancer research, there is emerging evidence showing these exosomes can load unique messages that reflect the condition of tumours and enables them to replicate and spread cancer more quickly through the body.

"Improving our understanding of how Alzheimer's and other diseases spread through exosomes will allow us to create new ways to treat and intervene in these cellular processes in the future."

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What evolution reveals about the function of bitter receptors

 To evaluate the chemical composition of food from a physiological point of view, it is important to know the functions of the receptors that interact with food ingredients. These include receptors for bitter compounds, which first evolved during evolution in bony fishes such as the coelacanth. What 400 million years of evolutionary history reveal about the function of both fish and human bitter receptors was recently published in the journal Genome Biology and Evolution by a team of researchers led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich and the University of Cologne.

Evolutionarily, bitter receptors are a relatively recent invention of nature compared to other chemoreceptors, such as olfactory receptors. Their function of protecting vertebrates from consuming potentially toxic substances has long been scientifically recognized. More recent are observations that bitter receptors have other functions beyond taste perception. These include roles in defense against pathogenic bacteria, in metabolic regulation, and possibly also functions as sensors for endogenous metabolites and hormones.

Coelacanth and zebrafish in comparison

The team of scientists led by biologists Sigrun Korsching of the University of Cologne and Maik Behrens of the Leibniz Institute for Food Systems Biology now provides further evidence to support this hypothesis. In their current study, the team compared two original bitter receptor types from the coelacanth (Latimeria chalumnae) with four others from the zebrafish (Danio rerio) phylogenetically, functionally and structurally. To this end, the research team conducted, among other experiments, extensive functional studies using an established cell-based test system as well as a computer-based modeling approach. The goal was to gain a deep insight into the evolutionary history of bitter receptors in order to learn more about their functions.

As the study results show, both fish species possess, amongst others, a pair of homologous bitter receptor genes that presumably arose from a primordial gene. In this regard, the bitter recognition spectra of these fish receptors were largely identical despite 400 million years of separate evolution, according to the results of the functional studies. "What is particularly exciting about our results is that the original fish receptors recognized substances in the cellular test system which are still detected by human bitter receptors to date. These include bile acids," says co-author Antonella Di Pizio of the Leibniz Institute.

Over 400 million years of selection pressure

"So there must have been selective pressure at least until humans evolved, that means human bitter receptors can still detect the same bitter substances as a bony fish did over 400 million years ago," concludes taste researcher Maik Behrens. Sigrun Korsching adds, "This speaks for one or more important functions of bitter receptors, even during human evolution."

"Coelacanths are carnivores. Therefore, one could speculate that the existence of a bitter receptor variant that mainly recognizes steroid hormones and bile acids protects against the consumption of poisonous fish, which can contain not only bile acids but also highly potent neurotoxins in their liver and gallbladder. For example, the poisonous puffer fish Arothron hispidus lives in the same waters as the coelacanth," says Maik Behrens. "In humans and also in zebrafish, however, it is questionable whether such a receptor variant would have been preserved from an evolutionary point of view if it did not have other functions inside the body. Another argument in favor of such extraoral functions is that bitter receptors are also found on human organs such as the heart, brain or thyroid gland," Behrens added. One goal of his research is to help understand the effects of bitter substances on a systems biological level, regardless of whether they entered the body through food or whether they belong to the body's own substances.

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Astronomers detect extended dark matter halo around ancient dwarf galaxy

 The Milky Way is surrounded by dozens of dwarf galaxies that are thought to be relics of the very first galaxies in the universe. Among the most primitive of these galactic fossils is Tucana II -- an ultrafaint dwarf galaxy that is about 50 kiloparsecs, or 163,000 light years, from Earth.

Now MIT astrophysicists have detected stars at the edge of Tucana II, in a configuration that is surprisingly far from its center but nevertheless caught up in the tiny galaxy's gravitational pull. This is the first evidence that Tucana II hosts an extended dark matter halo -- a region of gravitationally bound matter that the researchers calculated to be three to five times more massive than scientists had estimated. This discovery of far-flung stars in an ancient dwarf galaxy implies that the very first galaxies in the universe were also likely extended and more massive than previously thought.

"Tucana II has a lot more mass than we thought, in order to bound these stars that are so far away," says MIT graduate student Anirudh Chiti. "This means that other relic first galaxies probably have these kinds of extended halos too."

The researchers also determined that the stars on the outskirts of Tucana II are more primitive than the stars at the galaxy's core. This is the first evidence of such a stellar imbalance in an ultrafaint dwarf galaxy.

The unique configuration suggests that the ancient galaxy may have been the product of one of the first mergers in the universe, between two infant galaxies -- one slightly less primitive than the other.

"We may be seeing the first signature of galactic cannibalism," says Anna Frebel, the Silverman Family Career Development Associate Professor of Physics at MIT. "One galaxy may have eaten one of its slightly smaller, more primitive neighbors, that then spilled all its stars into the outskirts."

Frebel, Chiti, and their colleagues have published their results today in Nature Astronomy.

Not-so-wimpy galaxies

Tucana II is one of the most primitive dwarf galaxies known, based on the metal content of its stars. Stars with low metal content likely formed very early on, when the universe was not yet producing heavy elements. In the case of Tucana II, astronomers had previously identified a handful of stars around the galaxy's core with such low metal content that the galaxy was deemed the most chemically primitive of the known ultrafaint dwarf galaxies.

Chiti and Frebel wondered whether the ancient galaxy might harbor other, even older stars, that might shed light on the formation of the universe's first galaxies. To test this idea, they obtained observations of Tucana II through the SkyMapper Telescope, an optical ground-based telescope in Australia that takes in wide views of the southern sky.

The team used an imaging filter on the telescope to spot primitive, metal-poor stars beyond the galaxy's core. The team ran an algorithm, developed by Chiti, through the filtered data to efficiently pick out stars with low metal content, including the previously identified stars at the center and nine new stars much further out from the galactic core.

"Ani's analysis shows a kinematic conection, that these far-out stars move in lockstep with the inner stars, like bathwater going down the drain," Frebel adds.

The results suggest that Tucana II must have an extended dark matter halo that is three to five times more massive than previously thought, in order for it to keep a gravitational hold on these far-off stars. Dark matter is a hypothetical type of matter that is thought to make up more than 85 percent of the universe. Every galaxy is thought to be held together by a local concentration, or halo, of dark matter.

"Without dark matter, galaxies would just fly apart," Chiti. says. "[Dark matter] is a crucial ingredient in making a galaxy and holding it together."

The team's results are the first evidence that an ultrafaint dwarf galaxy can harbor an extended dark matter halo.

"This probably also means that the earliest galaxies formed in much larger dark matter halos than previously thought," Frebel says. "We have thought that the first galaxies were the tiniest, wimpiest galaxies. But they actually may have been several times larger than we thought, and not so tiny after all."

"A cannibalistic history"

Chiti and Frebel followed up their initial results with observations of Tucana II taken by the Magellan Telescopes in Chile. With Magellan, the team focused in on the galaxy's metal-poor stars to derive their relative metallicities, and discovered the outer stars were three times more metal-poor, and therefore more primitive, than those at the center.

"This is the first time we've seen something that looks like a chemical difference beween the inner and outer stars in an ancient galaxy," Chiti says.

A likely explanation for the imbalance may be an early galactic merger, in which a small galaxy -- possibly among the first generation of galaxies to form in the universe -- swallowed another nearby galaxy. This galactic cannibalism occurs constantly throughout the universe today, but it was unclear whether early galaxies merged in a similar way.

"Tucana II will eventually be eaten by the Milky Way, no mercy," Frebel says. "And it turns out this ancient galaxy may have its own cannibalistic history."

The team plans to use their approach to observe other ultrafaint dwarf galaxies around the Milky Way, in hopes of discovering even older, farther-flung stars.

"There are likely many more systems, perhaps all of them, that have these stars blinking in their outskirts," Frebel says.

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Searching for dark matter through the fifth dimension

 Theoretical physicists of the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz are working on a theory that goes beyond the Standard Model of particle physics and can answer questions where the Standard Model has to pass -- for example, with respect to the hierarchies of the masses of elementary particles or the existence of dark matter. The central element of the theory is an extra dimension in spacetime. Until now, scientists have faced the problem that the predictions of their theory could not be tested experimentally. They have now overcome this problem in a publication in the current issue of the European Physical Journal C.

As early as the 1920s, in an attempt to unify the forces of gravity and electromagnetism, Theodor Kaluza and Oskar Klein speculated about the existence of an extra dimension beyond the familiar three space dimensions and time -- which in physics are combined into 4-dimensional spacetime. If it exists, such a new dimension would have to be incredible tiny and unnoticeable to the human eye. In the late 1990s this idea has seen a remarkable renaissance, when it was realized that the existence of a fifth dimension could resolve some of the profound open questions of particle physics. In particular, Yuval Grossman of Stanford University and Matthias Neubert, then a professor at Cornell University, showed in a highly cited publication that the embedding of the Standard Model of particle physics in a 5-dimensional spacetime could explain the so far mysterious patterns seen in the masses of elementary particles.

Another 20 years later, the group of Matthias Neubert -- since 2006 on the faculty of Johannes Gutenberg University in Mainz (Germany) and spokesperson of the PRISMA+ Cluster of Excellence -- made another unexpected discovery: they found that the 5-dimensional field equations predicted the existence of a new, heavy particle with similar properties as the famous Higgs boson but a much heavier mass -- so heavy, in fact, that it cannot be produced even at the highest-energy particle collider in the world: the Large Hadron Collider (LHC) at the European Center for Nuclear Research CERN near Geneva (Switzerland). "It was a nightmare," recalls Javier Castellano Ruiz, a PhD student involved in the research, "we were excited by the idea that our theory predicts a new particle, but it appeared to be impossible to confirm this prediction in any foreseeable experiment."

The detour through the fifth dimension

In a recent paper published in the European Physical Journal C, the researchers found a spectacular resolution to this dilemma. They discovered that their proposed particle would necessarily mediate a new force between the known elementary particles (our visible universe) and the mysterious dark matter (the dark sector). Even the abundance of dark matter in the cosmos, as observed in astrophysical experiments, can be explained by their theory. This offers exciting new ways to search for the constituents of the dark matter -- literally via a detour through the extra dimension -- and obtain clues about the physics at a very early stage in the history of our universe, when the dark matter was produced. "After years of searching for possible confirmations of our theoretical predictions, we are now confident that the mechanism we have discovered would make the dark matter accessible to forthcoming experiments, because the properties of the new interaction between ordinary matter and dark matter -- which is mediated by our proposed particle -- can be calculated accurately within our theory" says Matthias Neubert, head of the research team. "In the end -- so our hope -- the new particle may be discovered first through its interactions with the dark sector." This example nicely illustrates the fruitful interplay between experimental and theoretical basic science -- a hallmark of the PRISMA+ Cluster of Excellence.

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How do electrons close to Earth reach almost the speed of light?

 New study found that electrons can reach ultra-relativistic energies for very special conditions in the magnetosphere when space is devoid of plasma.

Recent measurements from NASA's Van Allen Probes spacecraft showed that electrons can reach ultra-relativistic energies flying at almost the speed of light. Hayley Allison, Yuri Shprits and collaborators from the German Research Centre for Geosciences have revealed under which conditions such strong accelerations occur. They had already demonstrated in 2020 that during solar storm plasma waves play a crucial role for that. However, it was previously unclear why such high electron energies are not achieved in all solar storms. In the journal Science Advances, Allison, Shprits and colleagues now show that extreme depletions of the background plasma density are crucial.

Ultra-relativistic electrons in space

At ultra-relativistic energies, electrons move at almost the speed of light. Then the laws of relativity become most important. The mass of the particles increases by a factor ten, time is slowing down, and distance decreases. With such high energies, charged particles become most dangerous to even the best protected satellites. As almost no shielding can stop them, their charge can destroy sensitive electronics. Predicting their occurrence -- for example, as part of the observations of space weather practised at the GFZ -- is therefore very important for modern infrastructure.

To investigate the conditions for the enormous accelerations of the electrons, Allison and Shprits used data from a twin mission, the "Van Allen Probes," which the US space agency NASA had launched in 2012. The aim was to make detailed measurements in the radiation belt, the so-called Van Allen belt, which surrounds the Earth in a donut shape in terrestrial space. Here -- as in the rest of space -- a mixture of positively and negatively charged particles forms a so-called plasma. Plasma waves can be understood as fluctuations of the electric and magnetic field, excited by solar storms. They are an important driving force for the acceleration of electrons.

Data analysis with machine learning

During the mission, both solar storms that produced ultra-relativistic electrons and storms without this effect were observed. The density of the background plasma turned out to be a decisive factor for the strong acceleration: electrons with the ultra-relativistic energies were only observed to increase when the plasma density dropped to very low values of only about ten particles per cubic centimetre, while normally such density is five to ten times higher.

Using a numerical model that incorporated such extreme plasma depletion, the authors showed that periods of low density create preferential conditions for the acceleration of electrons -- from an initial few hundred thousand to more than seven million electron volts. To analyse the data from the Van Allen probes, the researchers used machine learning methods, the development of which was funded by the GEO.X network. They enabled the authors to infer the total plasma density from the measured fluctuations of electric and magnetic field.

The crucial role of plasma

"This study shows that electrons in the Earth's radiation belt can be promptly accelerated locally to ultra-relativistic energies, if the conditions of the plasma environment -- plasma waves and temporarily low plasma density -- are right. The particles can be regarded as surfing on plasma waves. In regions of extremely low plasma density they can just take a lot of energy from plasma waves. Similar mechanisms may be at work in the magnetospheres of the outer planets such as Jupiter or Saturn and in other astrophysical objects," says Yuri Shprits, head of the GFZ section Space physics and space weather and Professor at University of Potsdam.

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Finding rare birds is never a picnic, contrary to popular Patagonia belief

 One of birdwatching's most commonly held and colorfully named beliefs, the Patagonia Picnic Table Effect, is more a fun myth than a true phenomenon, Oregon State University research suggests.

Owing its moniker to an Arizona rest area, the Patagonia Picnic Table Effect, often shortened to PPTE, has for decades been cited as a key driver of behavior, and rare-species-finding success, among participants in the multibillion-dollar recreational birding business -- an industry that has gotten even stronger during a pandemic that's shut down so many other activities.

But a study led by an OSU College of Science graduate student shows that the PPTE -- which says that after a rare bird is spotted somewhere, birders flock to the area and then find additional rare species at an accelerated rate -- is not borne out by the data.

Findings were published in PeerJ.

"Birdwatching is one of the fastest growing recreational activities in the world," said OSU integrative biology Ph.D. student Jesse Laney. "The lure of finding very rare birds adds a level of excitement that draws birders even from distant locations."

The specifics of the Patagonia Picnic Table Effect's origin story have grown slightly murky over time, but its basic gist is engrained in birder lore.

Patagonia is a tiny town near the Arizona-Mexico border, and a nearby rest area gave rise to the picnic table part of the name. Sometime in the 1960s or 1970s, birders saw a rare black-capped gnatcatcher, or possibly a nesting pair of rose-throated becards, at the rest area.

Whichever it was, or whether it was something else entirely, word began to spread and birders began descending on Patagonia, which led to other interesting sightings, among them the thick-billed kingbird, five-striped sparrow and yellow grosbeak. The rest area remains a pilgrimage location for birdwatchers.

"It is anecdotal that when rare species are reported, increased activity by birders attempting to add rarities to their personal lists leads to the discovery of additional rare birds," Laney said. "The U.S. birdwatching community has been a big subscriber to the Patagonia Picnic Table Effect -- it's something they really believe in."

Laney and collaborators in the OSU College of Agricultural Sciences and at Cornell University examined the PPTE's veracity by analyzing a decade's worth of information in eBird, an online, public bird observation database maintained by Cornell.

"We wanted to know how often a discovery of one rare bird draws so many birders to a place that even more rarities are discovered?" Laney said. "We found that birders had no better chance of finding additional rarities at locations where a rare species had been discovered than they did when searching elsewhere for rare species. In a nutshell we found little support for the Patagonia Picnic Table Effect and therefore have to consider it a myth -- while acknowledging that it is a really fun myth."

Laney and collaborators Tyler Hallman and W. Douglas Robinson of the College of Agricultural Sciences and OSU alumna Jenna Curtis, now a staff member at Cornell, focused on sightings of North American "mega-rarities," 81 of the hardest-to-spot bird species on the continent -- all were rated as 4 or 5 on the American Birding Association's five-point rarity scale.

The scientists looked at 273 mega-rarity discoveries involving those 81 birds over 10 years starting in 2008, and the ensuing "draw and decay" -- birders descending on an area following a sighting, and then the tapering off of birding activity after the draw peaks. The mega-rarity events included a northern lapwing in Maine in 2013, a Eurasian hobby on Washington's Olympic Peninsula in 2014, and a streak-backed oriole at Carlsbad Caverns National Park in 2015.

"Across those 273 mega-rarity events, eBird data show that birder effort increased above the pre-event baseline level," Laney said. "The power of rare species to draw attention of birders was influenced by locational factors such as latitude and proximity to an airport, and by the year in which events took place."

The speed with which birders lost interest in seeking each rarity -- the decay rate -- was influenced by how long those rare birds continued to be detected, he added.

"Still, the decay rate was pretty variable among those events," Laney said. "We found no indication that draw was influenced by species identity or rarity level. To us, this suggests that mega-rarities have a profound influence on the behavior of birders simply by virtue of being very rare."

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Desktop PCs run simulations of mammals' brains

 University of Sussex academics have established a method of turbocharging desktop PCs to give them the same capability as supercomputers worth tens of millions of pounds.

Dr James Knight and Prof Thomas Nowotny from the University of Sussex's School of Engineering and Informatics used the latest Graphical Processing Units (GPUs) to give a single desktop PC the capacity to simulate brain models of almost unlimited size.

The researchers believe the innovation, detailed in Nature Computational Science, will make it possible for many more researchers around the world to carry out research on large-scale brain simulation, including the investigation of neurological disorders.

Currently, the cost of supercomputers is so prohibitive they are only affordable to very large institutions and government agencies and so are not accessible for large numbers of researchers.

As well as shaving tens of millions of pounds off the costs of a supercomputer, the simulations run on the desktop PC require approximately 10 times less energy bringing a significant sustainability benefit too.

Dr Knight, Research Fellow in Computer Science at the University of Sussex, said: "I think the main benefit of our research is one of accessibility. Outside of these very large organisations, academics typically have to apply to get even limited time on a supercomputer for a particular scientific purpose. This is quite a high barrier for entry which is potentially holding back a lot of significant research.

"Our hope for our own research now is to apply these techniques to brain-inspired machine learning so that we can help solve problems that biological brains excel at but which are currently beyond simulations.

"As well as the advances we have demonstrated in procedural connectivity in the context of GPU hardware, we also believe that there is also potential for developing new types of neuromorphic hardware built from the ground up for procedural connectivity. Key components could be implemented directly in hardware which could lead to even more truly significant compute time improvements."

The research builds on the pioneering work of US researcher Eugene Izhikevich who pioneered a similar method for large-scale brain simulation in 2006.

At the time, computers were too slow for the method to be widely applicable meaning simulating large-scale brain models has until now only been possible for a minority of researchers privileged to have access to supercomputer systems.

The researchers applied Izhikevich's technique to a modern GPU, with approximately 2,000 times the computing power available 15 years ago, to create a cutting-edge model of a Macaque's visual cortex (with 4.13 × 106 neurons and 24.2 × 109 synapse) which previously could only be simulated on a supercomputer.

The researchers' GPU accelerated spiking neural network simulator uses the large amount of computational power available on a GPU to 'procedurally' generate connectivity and synaptic weights 'on the go' as spikes are triggered -- removing the need to store connectivity data in memory.

Initialization of the researchers' model took six minutes and simulation of each biological second took 7.7 min in the ground state and 8.4 min in the resting state- up to 35 % less time than a previous supercomputer simulation. In 2018, one rack of an IBM Blue Gene/Q supercomputer initialization of the model took around five minutes and simulating one second of biological time took approximately 12 minutes.

Prof Nowotny, Professor of Informatics at the University of Sussex, said: "Large-scale simulations of spiking neural network models are an important tool for improving our understanding of the dynamics and ultimately the function of brains. However, even small mammals such as mice have on the order of 1 × 1012 synaptic connections meaning that simulations require several terabytes of data -- an unrealistic memory requirement for a single desktop machine.

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Gendered division of labor shaped human spatial behavior

 Navigating, exploring and thinking about space are part of daily life, whether it's carving a path through a crowd, hiking a backcountry trail or maneuvering into a parking spot.

For most of human history, the driving force for day-to-day wayfinding and movement across the landscape was a need for food. And unlike other primates, our species has consistently divided this labor along gender lines.

In new research published in Nature Human Behaviour, scientists including James Holland Jones of Stanford and lead author Brian Wood of University of California, Los Angeles, argue that the increasingly gendered division of labor in human societies during the past 2.5 million years dramatically shaped how our species uses space, and possibly how we think about it.

Underlying these conclusions is a huge and detailed trove of travel data revealing stark differences in the ways men and women among the nomadic Hadza people of Tanzania use space. A contemporary hunter-gatherer society, the Hadza provide a window into a highly mobile lifestyle, which was the norm for our species before the widespread adoption of agriculture.

"We're taking gender differences as a given in this particular cultural setting, and then asking what consequences they have downstream," said Jones, an associate professor of Earth system science at Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth) and a senior fellow at Stanford Woods Institute for the Environment.

A better understanding of this dynamic could yield clues about why men and women seem to think about space differently. Research in many human populations suggests men and women are better at different types of spatial tasks. On average, women tend to excel on spatial memory tasks, while men tend to score higher on two basic measures of spatial cognition associated with movement: mental rotation of objects and accurately pointing to distant locations.

'Male work is more navigationally challenging'

The paper examines a popular theory that men's hunting for wild game would produce more extensive and sinuous travel, and that women's harvesting of plant foods would lead to more concentrated, straight-line travel to and from known locations.

While previous efforts to substantiate the theory have relied heavily on verbal accounts, the researchers here tested it by examining more than 13,000 miles of travel logged on lightweight GPS trackers worn by Hadza foragers between 2005 and 2018. "One or two researchers would walk through camp early in the morning as people were rousing," the authors write. "We would greet people at their homes or hearths and hand out GPS devices to be worn during the day."

Around nightfall, when most people had returned to camp, Wood and assistants hired in the Hadza community removed the devices. They ultimately used data from 179 people, representing 15 camps and ranging in age from two to 84 years old.

The authors also examined the degree of overlap in the lands visited by men and women. "One of the most surprising results of this study was the fact that Hadza men and women essentially occupy different worlds from a young age. In our data, most of the landscape was effectively gender-segregated," said Wood, an assistant professor of anthropology at UCLA who began working on this paper a decade ago as a postdoctoral scholar at Stanford.

To analyze the movement data, the researchers adopted techniques from the field of movement ecology and also developed custom software. As expected, the results show men walked further per day, covered more land in less direct paths and were more likely to travel alone. "In this hunting and gathering context, male work is more navigationally challenging," the researchers write.

Although some individual day journeys extended to 20 miles or more, Hadza men overall averaged eight miles per day and women -- many of them accompanied by young children -- averaged nearly five miles. Gender differences emerged by the age of six. From the mid-forties, the gender difference declined, mostly due to decreasing travel by men while women sustained more of their daily mileage.

Human mobility in a changing world

Detailed spatial data like those amassed in this study will aid future comparative research into human mobility, according to the authors. This holds particular resonance in light of a pandemic that has forced sudden revisions of normal movement patterns and heightened attention to the costs and benefits of different spatial habits.

Already, Wood has begun to apply technical, logistical and scientific lessons from this study to a new National Science Foundation project meant to help identify research and policy priorities to prepare the U.S. for inevitable future pandemics -- in part by measuring mobility and modeling patterns of social interaction. "The study of human movement can be used to identify at-risk communities for disease transmission and spread," Wood explained.

Even when we're not in a pandemic, Jones said, people's mobility drives economic activity, social cohesion and environmental impacts. And the environment, in turn, shapes spatial behavior. That feedback loop is at the heart of some of the internal migration patterns already emerging as a response to global warming. As once-rare weather events become commonplace, Jones explained, migrant laborers will likely travel longer distances for work; more people will engage in seasonal migration to pursue agricultural work or escape hurricanes and droughts, and crop failures will drive more rural residents to urban areas.

"Changing mobility is going to be one of the key ways that humans adapt to a heated world," Jones said. "Knowing more about gender differences and other drivers for spatial behaviors across a wide swath of human populations and ecological contexts will help us anticipate how this adaptation will play out and inform policies to manage it."

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How the brain is programmed for computer programming?

 Countries around the world are seeing a surge in the number of computer science students. Enrolment in related university programs in the U.S. and Canada tripled between 2006-2016 and Europe too has seen rising numbers. At the same time, the age to start coding is becoming younger and younger because governments in many different countries are pushing K-12 computer science education. Despite the increasing popularity of computer programming, little is known about how our brains adapt to this relatively new activity. A new study by researchers in Japan has examined the brain activity of thirty programmers of diverse levels of expertise, finding that seven regions of the frontal, parietal and temporal cortices in expert programmer's brain are fine-tuned for programming. The finding suggests that higher programming skills are built upon fine-tuned brain activities on a network of multiple distributed brain regions.

"Many studies have reported differences between expert and novice programmers in behavioural performance, knowledge structure and selective attention. What we don't know is where in the brain these differences emerge," says Takatomi Kubo, an associate professor at Nara Institute of Science and Technology, Japan, and one of the lead authors of the study.

To answer this question, the researchers observed groups of novices, experienced, and expert programmers. The programmers were shown 72 different code snippets while under the observation of functional MRI (fMRI) and asked to place each snippet into one of four functional categories. As expected, programmers with higher skills were better at correctly categorizing the snippets. A subsequent searchlight analysis revealed that the amount of information in seven brain regions strengthened with the skill level of the programmer: the bilateral inferior frontal gyrus pars triangularis (IFG Tri), left inferior parietal lobule (IPL), left supramarginal gyrus (SMG), left middle and inferior temporal gyri (MTG/IT), and right middle frontal gyrus (MFG).

"Identifying these characteristics in expert programmers' brains offers a good starting point for understanding the cognitive mechanisms behind programming expertise. Our findings illuminate the potential set of cognitive functions constituting programming expertise," Kubo says.

More specifically, the left IFG Tri and MTG are known to be associated with natural language processing and, in particular, semantic knowledge retrieval in a goal-oriented way. The left IPL and SMG are associated with episodic memory retrieval. The right MFG and IFG Tri are functionally related to stimulus-driven attention control.

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