13 young adults with tetraplegia are able to feed themselves, hold a drink, brush their teeth, and write as a result of a novel surgical technique which connects functioning nerves with injured nerves to restore power in paralysed muscles Nerve transfer surgery has enabled 13 young adults with complete paralysis to regain movement and function in their elbows and hands, according to the largest case series of this technique in people with tetraplegia (paralysis of both the upper and lower limbs), published in The Lancet.
During the surgery, Australian surgeons attached functioning nerves above the spinal injury to paralysed nerves below the injury. Two years after surgery, and following intensive physical therapy, participants were able to reach their arm out in front of them and open their hand to pick up and manipulate objects. Restoring elbow extension improved their ability to propel their wheelchair and to transfer into bed or a car.
They can now perform everyday tasks independently such as feeding themselves, brushing teeth and hair, putting on make-up, writing, handling money and credit cards, and using tools and electronic devices.
The findings suggest that nerve transfers can achieve similar functional improvements to traditional tendon transfers, with the benefit of smaller incisions and shorter immobilisation times after surgery.
In 10 participants, nerve transfers were uniquely combined with tendon transfers allowing different styles of reconstruction to be performed in each hand, and enabling participants to benefit from the innate strengths of both tendon and nerve transfers. Nerve transfers restored more natural movement and finer motor control in one hand, and tendon transfers restored more power and heavy lifting ability in the other hand.
While only a small study, researchers say that nerve transfers are a major advance in the restoration of hand and arm function, and offer another safe, reliable surgical option for people living with tetraplegia.
Nevertheless, four nerve transfers failed in three participants and the authors conclude that more research will be needed to determine which people are the best candidates to select for nerve transfer surgery to minimise the incidence of failure.
"For people with tetraplegia, improvement in hand function is the single most important goal. We believe that nerve transfer surgery offers an exciting new option, offering individuals with paralysis the possibility of regaining arm and hand functions to perform everyday tasks, and giving them greater independence and the ability to participate more easily in family and work life," says Dr Natasha van Zyl from Austin Health in Melbourne, Australia who led the research.
"What's more, we have shown that nerve transfers can be successfully combined with traditional tendon transfer techniques to maximise benefits. When grasp and pinch was restored using nerve transfers in one hand and tendon transfers in the other, participants consistently reporting that they liked both hands for different reasons and would not choose to have two hands reconstructed in the same way."
Traditionally, upper limb function has been reconstructed using tendon transfer surgery, during which muscles that still work, but are designed for another function, are surgically re-sited to do the work of muscles that are paralysed. In contrast, nerve transfers allow the direct reanimation of the paralysed muscle itself. Additionally, nerve transfers can re-animate more than one muscle at a time, have a shorter period of immobilisation after surgery (10 days in a sling vs 6-12 weeks in a brace for a nerve transfer for elbow extension), and avoid the technical problems associated with of tendon transfer surgery including tendon tensioning during surgery and mechanical failure (stretch or rupture) after surgery.
Previous single case reports and small retrospective studies have shown nerve transfer surgery to be feasible and safe in people with tetraplegia. But this is the first prospective study to use standardised functional outcome measures and combinations of multiple nerve and tendon transfer surgeries.
In total the study recruited 16 young adults (average age 27 years) with traumatic, early (less than 18 months post injury) spinal cord injury to the neck (C5-C7), who were referred to Austin Health in Melbourne for restoration of function in the upper limb. Most were the result of motor vehicle accidents or sports injuries.
Participants underwent single or multiple nerve transfers in one or both upper limbs to restore elbow extension, grasp, pinch, and hand opening. This involved taking working nerves to expendable muscles innervated above the spinal injury and attaching them to the nerves of paralysed muscles innervated below the injury to restore voluntary control and reanimate the paralysed muscle.
For example, the surgeons selected the nerve supplying the teres minor muscle in the shoulder as a donor nerve and attached it to the nerve supplying the triceps that activates the muscles that extend (straighten) the elbow. To restore grasp and pinch the nerve to a spare wrist extensor muscle was transferred to the anterior interosseous nerve.
In total, 59 nerve transfers were completed in 16 participants (13 men and three women; 27 limbs). In 10 participants (12 limbs), nerve transfers were combined with tendon transfers to improve hand function.
Participants completed assessments on their level of independence related to activities of daily living (e.g., self-care, toilet, upper limb function, muscle power, grasp and pinch strength, and hand opening ability) before surgery, one year after surgery, and again two years later. Two participants were lost to follow up, and there was one death (unrelated to the surgery).
At 24 months, significant improvements were noted in the hands ability to pick up and release several objects within a specified time frame and independence. Prior to surgery, none of the participants were able to score on the grasp or pinch strength tests, but 2 years later pinch and grasp strength were high enough to perform most activities of daily living.
Three participants had four failed nerve transfers -- two had a permanent decrease in sensation, and two had a temporary decrease in wrist strength that resolved by 1 year after surgery. Overall, surgery was well tolerated. Five serious adverse events were recorded (including a fall from a wheelchair with femur fracture), but none were related to the surgery.
Despite these achievements, nerve transfer surgery still has some limitations. For the best results nerve transfers should ideally be performed within 6-12 months of injury. Additionally, it can take months after nerve transfer for nerve regrowth into the paralysed muscle to occur and for new movement to be seen, and years until full strength is achieved. However, the authors note that one of the benefits of nerve transfers is that most movements not successfully restored by nerve transfers can still be restored using tendon transfers.
Read more at Science Daily
Jul 6, 2019
First observation of native ferroelectric metal
In a paper released today in Science Advances, UNSW researchers describe the first observation of a native ferroelectric metal.
The study represents the first example of a native metal with bistable and electrically switchable spontaneous polarization states -- the hallmark of ferroelectricity.
"We found coexistence of native metallicity and ferroelectricity in bulk crystalline tungsten ditelluride (WTe2) at room temperature," explains study author Dr Pankaj Sharma.
"We demonstrated that the ferroelectric state is switchable under an external electrical bias and explain the mechanism for 'metallic ferroelectricity' in WTe2 through a systematic study of the crystal structure, electronic transport measurements and theoretical considerations."
"A van der Waals material that is both metallic and ferroelectric in its bulk crystalline form at room temperature has potential for new nano-electronics applications," says author Dr Feixiang Xiang.
FERROELECTRIC BACKGROUNDER
Ferroelectricity can be considered an analogy to ferromagnetism. A ferromagnetic material displays permanent magnetism, and in layperson's terms, is simply, a 'magnet' with north and south pole. Ferroelectric material likewise displays an analogous electrical property called a permanent electric polarisation, which originates from electric dipoles consisting of equal, but oppositely charged ends or poles. In ferroelectric materials, these electric dipoles exist at the unit cell level and give rise to a non-vanishing permanent electric dipole moment.
This spontaneous electric dipole moment can be repeatedly transitioned between two or more equivalent states or directions upon application of an external electric field -- a property utilised in numerous ferroelectric technologies, for example nano-electronic computer memory, RFID cards, medical ultrasound transducers, infrared cameras, submarine sonar, vibration and pressure sensors, and precision actuators.
Conventionally, ferroelectricity has been observed in materials that are insulating or semiconducting rather than metallic, because conduction electrons in metals screen-out the static internal fields arising from the dipole moment.
THE STUDY
A room-temperature ferroelectric semimetal was published in Science Advances in July 2019.
Bulk single-crystalline tungsten ditelluride (WTe2), which belongs to a class of materials known as transition metal dichalcogenides (TMDCs), was probed by spectroscopic electrical transport measurements, conductive-atomic force microscopy (c-AFM) to confirm its metallic behaviour, and by piezo-response force microscopy (PFM) to map the polarisation, detecting lattice deformation due to an applied electric field.
Ferroelectric domains -- ie, the regions with oppositely oriented direction of polarization -- were directly visualised in freshly-cleaved WTe2 single crystals.
Spectroscopic-PFM measurements with top electrode in a capacitor geometry was used to demonstrate switching of the ferroelectric polarization.
The study was supported by funding from the Australian Research Council through the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), and the work was performed in part using facilities of the NSW Nodes of the Australian National Fabrication Facility, with the assistance of the Australian Government Research Training Program Scholarship scheme.
First-principles density functional theory (DFT) calculations (University of Nebraska) confirmed the experimental findings of the electronic and structural origins of the ferroelectric instability of WTe2, supported by the National Science Foundation.
FERROELECTRIC STUDIES AT FLEET
Ferroelectric materials are keenly studied at FLEET (the ARC Centre of Excellence in Future Low-Energy Electronics Technologies) for their potential use in low-energy electronics, 'beyond CMOS' technology.
The switchable electric dipole moment of ferroelectric materials could for example be used as a gate for the underlying 2D electron system in an artificial topological insulator.
In comparison with conventional semiconductors, the very close (sub-nanometre) proximity of a ferroelectric's electron dipole moment to the electron gas in the atomic crystal ensures more effective switching, overcoming limitations of conventional semiconductors where the conducting channel is buried tens of nanometres below the surface.
Read more at Science Daily
The study represents the first example of a native metal with bistable and electrically switchable spontaneous polarization states -- the hallmark of ferroelectricity.
"We found coexistence of native metallicity and ferroelectricity in bulk crystalline tungsten ditelluride (WTe2) at room temperature," explains study author Dr Pankaj Sharma.
"We demonstrated that the ferroelectric state is switchable under an external electrical bias and explain the mechanism for 'metallic ferroelectricity' in WTe2 through a systematic study of the crystal structure, electronic transport measurements and theoretical considerations."
"A van der Waals material that is both metallic and ferroelectric in its bulk crystalline form at room temperature has potential for new nano-electronics applications," says author Dr Feixiang Xiang.
FERROELECTRIC BACKGROUNDER
Ferroelectricity can be considered an analogy to ferromagnetism. A ferromagnetic material displays permanent magnetism, and in layperson's terms, is simply, a 'magnet' with north and south pole. Ferroelectric material likewise displays an analogous electrical property called a permanent electric polarisation, which originates from electric dipoles consisting of equal, but oppositely charged ends or poles. In ferroelectric materials, these electric dipoles exist at the unit cell level and give rise to a non-vanishing permanent electric dipole moment.
This spontaneous electric dipole moment can be repeatedly transitioned between two or more equivalent states or directions upon application of an external electric field -- a property utilised in numerous ferroelectric technologies, for example nano-electronic computer memory, RFID cards, medical ultrasound transducers, infrared cameras, submarine sonar, vibration and pressure sensors, and precision actuators.
Conventionally, ferroelectricity has been observed in materials that are insulating or semiconducting rather than metallic, because conduction electrons in metals screen-out the static internal fields arising from the dipole moment.
THE STUDY
A room-temperature ferroelectric semimetal was published in Science Advances in July 2019.
Bulk single-crystalline tungsten ditelluride (WTe2), which belongs to a class of materials known as transition metal dichalcogenides (TMDCs), was probed by spectroscopic electrical transport measurements, conductive-atomic force microscopy (c-AFM) to confirm its metallic behaviour, and by piezo-response force microscopy (PFM) to map the polarisation, detecting lattice deformation due to an applied electric field.
Ferroelectric domains -- ie, the regions with oppositely oriented direction of polarization -- were directly visualised in freshly-cleaved WTe2 single crystals.
Spectroscopic-PFM measurements with top electrode in a capacitor geometry was used to demonstrate switching of the ferroelectric polarization.
The study was supported by funding from the Australian Research Council through the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), and the work was performed in part using facilities of the NSW Nodes of the Australian National Fabrication Facility, with the assistance of the Australian Government Research Training Program Scholarship scheme.
First-principles density functional theory (DFT) calculations (University of Nebraska) confirmed the experimental findings of the electronic and structural origins of the ferroelectric instability of WTe2, supported by the National Science Foundation.
FERROELECTRIC STUDIES AT FLEET
Ferroelectric materials are keenly studied at FLEET (the ARC Centre of Excellence in Future Low-Energy Electronics Technologies) for their potential use in low-energy electronics, 'beyond CMOS' technology.
The switchable electric dipole moment of ferroelectric materials could for example be used as a gate for the underlying 2D electron system in an artificial topological insulator.
In comparison with conventional semiconductors, the very close (sub-nanometre) proximity of a ferroelectric's electron dipole moment to the electron gas in the atomic crystal ensures more effective switching, overcoming limitations of conventional semiconductors where the conducting channel is buried tens of nanometres below the surface.
Read more at Science Daily
Jul 5, 2019
More 'reactive' land surfaces cooled the Earth down
From time to time, there have been long periods of cooling in Earth's history. Temperatures had already fallen for more than ten million years before the last ice age began about 2.5 million years ago. At that time the northern hemisphere was covered with massive ice masses and glaciers. A geoscientific paradigm, widespread for over twenty years, explains this cooling with the formation of the large mountain ranges such as the Andes, the Himalayas and the Alps. As a result, more rock weathering has taken place, the paradigm suggests. This in turn removed more carbon dioxide (CO2) from the atmosphere, so that the 'greenhouse effect' decreased and the atmosphere cooled. This and other processes eventually led to the 'ice Age'.
In a new study, Jeremy Caves-Rugenstein from ETH Zurich, Dan Ibarra from Stanford University and Friedhelm von Blanckenburg from the GFZ German Research Centre for Geosciences in Potsdam were able to show that this paradigm cannot be upheld. According to the paper, weathering was constant over the period under consideration. Instead, increased 'reactivity' of the land surface has led to a decrease in CO2 in the atmosphere, thus cooling the Earth. The researchers published the results in the journal Nature.
A second look after isotope analysis
The process of rock weathering, and especially the chemical weathering of rocks with carbonic acid, has controlled the Earth's climate for billions of years. Carbonic acid is produced from CO2 when it dissolves in rainwater. Weathering thus removes CO2 from the Earth's atmosphere, precisely to the extent that volcanic gases supplied the atmosphere with it. The paradigm that has been widespread so far states that with the formation of the large mountains ranges in the last 15 million years, erosion processes have increased -- and with them also the CO2-binding rock weathering. Indeed, geochemical measurements in ocean sediments show that the proportion of CO2 in the atmosphere has strongly decreased during this phase.
"The hypothesis, however, has a big catch," explains Friedhelm von Blanckenburg of GFZ. "If the atmosphere had actually lost as much CO2 as the weathering created by erosion would have caused, it would hardly have had any CO2 left after less than a million years. All water would have had frozen to ice and life would have had a hard time to survive. But that was not the case."
That these doubts are justified, was already shown by von Blanckenburg and his colleague Jane Willenbring in a 2010 study, which appeared in Nature likewise. "We used measurements of the rare isotope beryllium-10 produced by cosmic radiation in the Earth's atmosphere and its ratio to the stable isotope beryllium-9 in ocean sediment to show that the weathering of the land surface had not increased at all," says Friedhelm von Blanckenburg.
The land's surface has become more 'reactive'
In the study published now, Caves-Rugenstein, Ibarra and von Blanckenburg additionally used the data of stable isotopes of the element lithium in ocean sediments as an indicator for the weathering processes. They wanted to find out how, despite constant rock weathering, the amount of CO2 in the atmosphere could have decreased. They entered their data into a computer model of the global carbon cycle.
Indeed, the results of the model showed that the potential of the land surface to weather has increased, but not the speed at which it weathered. The researchers call this potential of weathering the 'reactivity' of the land surface. "Reactivity describes how easily chemical compounds or elements take part in a reaction," explains Friedhelm von Blanckenburg. If there are more non-weathered and therefore more reactive rocks at the surface, these can in total react as extensively chemically with little CO2 in the atmosphere as already heavily weathered rocks would do with a lot of CO2. The decrease in CO2 in the atmosphere, which is responsible for the cooling, can thus be explained without an increased speed of weathering.
Read more at Science Daily
In a new study, Jeremy Caves-Rugenstein from ETH Zurich, Dan Ibarra from Stanford University and Friedhelm von Blanckenburg from the GFZ German Research Centre for Geosciences in Potsdam were able to show that this paradigm cannot be upheld. According to the paper, weathering was constant over the period under consideration. Instead, increased 'reactivity' of the land surface has led to a decrease in CO2 in the atmosphere, thus cooling the Earth. The researchers published the results in the journal Nature.
A second look after isotope analysis
The process of rock weathering, and especially the chemical weathering of rocks with carbonic acid, has controlled the Earth's climate for billions of years. Carbonic acid is produced from CO2 when it dissolves in rainwater. Weathering thus removes CO2 from the Earth's atmosphere, precisely to the extent that volcanic gases supplied the atmosphere with it. The paradigm that has been widespread so far states that with the formation of the large mountains ranges in the last 15 million years, erosion processes have increased -- and with them also the CO2-binding rock weathering. Indeed, geochemical measurements in ocean sediments show that the proportion of CO2 in the atmosphere has strongly decreased during this phase.
"The hypothesis, however, has a big catch," explains Friedhelm von Blanckenburg of GFZ. "If the atmosphere had actually lost as much CO2 as the weathering created by erosion would have caused, it would hardly have had any CO2 left after less than a million years. All water would have had frozen to ice and life would have had a hard time to survive. But that was not the case."
That these doubts are justified, was already shown by von Blanckenburg and his colleague Jane Willenbring in a 2010 study, which appeared in Nature likewise. "We used measurements of the rare isotope beryllium-10 produced by cosmic radiation in the Earth's atmosphere and its ratio to the stable isotope beryllium-9 in ocean sediment to show that the weathering of the land surface had not increased at all," says Friedhelm von Blanckenburg.
The land's surface has become more 'reactive'
In the study published now, Caves-Rugenstein, Ibarra and von Blanckenburg additionally used the data of stable isotopes of the element lithium in ocean sediments as an indicator for the weathering processes. They wanted to find out how, despite constant rock weathering, the amount of CO2 in the atmosphere could have decreased. They entered their data into a computer model of the global carbon cycle.
Indeed, the results of the model showed that the potential of the land surface to weather has increased, but not the speed at which it weathered. The researchers call this potential of weathering the 'reactivity' of the land surface. "Reactivity describes how easily chemical compounds or elements take part in a reaction," explains Friedhelm von Blanckenburg. If there are more non-weathered and therefore more reactive rocks at the surface, these can in total react as extensively chemically with little CO2 in the atmosphere as already heavily weathered rocks would do with a lot of CO2. The decrease in CO2 in the atmosphere, which is responsible for the cooling, can thus be explained without an increased speed of weathering.
Read more at Science Daily
How trees could save the climate
The Crowther Lab at ETH Zurich investigates nature-based solutions to climate change. In their latest study the researchers showed for the first time where in the world new trees could grow and how much carbon they would store. Study lead author and postdoc at the Crowther Lab Jean-François Bastin explains: "One aspect was of particular importance to us as we did the calculations: we ex-cluded cities or agricultural areas from the total restoration potential as these areas are needed for hu-man life."
Reforest an area the size of the USA
The researchers calculated that under the current climate conditions, Earth's land could support 4.4 billion hectares of continuous tree cover. That is 1.6 billion more than the currently existing 2.8 billion hectares. Of these 1.6 billion hectares, 0.9 billion hectares fulfill the criterion of not being used by hu-mans. This means that there is currently an area of the size of the US available for tree restoration. Once mature, these new forests could store 205 billion tonnes of carbon: about two thirds of the 300 billion tonnes of carbon that has been released into the atmosphere as a result of human activity since the Industrial Revolution.
According to Prof. Thomas Crowther, co-author of the study and founder of the Crowther Lab at ETH Zurich: "We all knew that restoring forests could play a part in tackling climate change, but we didn't really know how big the impact would be. Our study shows clearly that forest restoration is the best climate change solution available today. But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage."
Russia best suited for reforestation
The study also shows which parts of the world are most suited to forest restoration. The greatest po-tential can be found in just six countries: Russia (151 million hectares); the US (103 million hectares); Canada (78.4 million hectares); Australia (58 million hectares); Brazil (49.7 million hectares); and China (40.2 million hectares).
Many current climate models are wrong in expecting climate change to increase global tree cover, the study warns. It finds that there is likely to be an increase in the area of northern boreal forests in re-gions such as Siberia, but tree cover there averages only 30 to 40 percent. These gains would be out-weighed by the losses suffered in dense tropical forests, which typically have 90 to 100 percent tree cover.
Look at Trees!
A tool on the Crowther Lab website enables users to look at any point on the globe, and find out how many trees could grow there and how much carbon they would store. It also offers lists of for-est restoration organisations. The Crowther Lab will also be present at this year's Scientifica (web-site available in German only) to show the new tool to visitors.
Read more at Science Daily
Reforest an area the size of the USA
The researchers calculated that under the current climate conditions, Earth's land could support 4.4 billion hectares of continuous tree cover. That is 1.6 billion more than the currently existing 2.8 billion hectares. Of these 1.6 billion hectares, 0.9 billion hectares fulfill the criterion of not being used by hu-mans. This means that there is currently an area of the size of the US available for tree restoration. Once mature, these new forests could store 205 billion tonnes of carbon: about two thirds of the 300 billion tonnes of carbon that has been released into the atmosphere as a result of human activity since the Industrial Revolution.
According to Prof. Thomas Crowther, co-author of the study and founder of the Crowther Lab at ETH Zurich: "We all knew that restoring forests could play a part in tackling climate change, but we didn't really know how big the impact would be. Our study shows clearly that forest restoration is the best climate change solution available today. But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage."
Russia best suited for reforestation
The study also shows which parts of the world are most suited to forest restoration. The greatest po-tential can be found in just six countries: Russia (151 million hectares); the US (103 million hectares); Canada (78.4 million hectares); Australia (58 million hectares); Brazil (49.7 million hectares); and China (40.2 million hectares).
Many current climate models are wrong in expecting climate change to increase global tree cover, the study warns. It finds that there is likely to be an increase in the area of northern boreal forests in re-gions such as Siberia, but tree cover there averages only 30 to 40 percent. These gains would be out-weighed by the losses suffered in dense tropical forests, which typically have 90 to 100 percent tree cover.
Look at Trees!
A tool on the Crowther Lab website enables users to look at any point on the globe, and find out how many trees could grow there and how much carbon they would store. It also offers lists of for-est restoration organisations. The Crowther Lab will also be present at this year's Scientifica (web-site available in German only) to show the new tool to visitors.
Read more at Science Daily
Camera brings unseen world to light
When the first full-length movie made with the advanced, three-color process of Technicolor premiered in 1935, The New York Times declared "it produced in the spectator all the excitement of standing upon a peak ... and glimpsing a strange, beautiful and unexpected new world."
Technicolor forever changed how cameras -- and people -- saw and experienced the world around them. Today, there is a new precipice -- this one, offering views of a polarized world.
Polarization, the direction in which light vibrates, is invisible to the human eye (but visible to some species of shrimp and insects). But it provides a great deal of information about the objects with which it interacts. Cameras that see polarized light are currently used to detect material stress, enhance contrast for object detection, and analyze surface quality for dents or scratches.
However, like the early color cameras, current-generation polarization-sensitive cameras are bulky. Moreover, they often rely on moving parts and are costly, severely limiting the scope of their potential application.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a highly compact, portable camera that can image polarization in a single shot. The miniature camera -- about the size of a thumb -- could find a place in the vision systems of autonomous vehicles, onboard planes or satellites to study atmospheric chemistry, or be used to detect camouflaged objects.
The research is published in Science.
"This research is game-changing for imaging," said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper. "Most cameras can typically only detect the intensity and color of light but can't see polarization. This camera is a new eye on reality, allowing us to reveal how light is reflected and transmitted by the world around us."
"Polarization is a feature of light that is changed upon reflection off a surface," said Paul Chevalier, a postdoctoral fellow at SEAS and co-author of the study. "Based on that change, polarization can help us in the 3D reconstruction of an object, to estimate its depth, texture and shape, and to distinguish man-made objects from natural ones, even if they're the same shape and color."
To unlock that powerful world of polarization, Capasso and his team harnessed the potential of metasurfaces, nanoscale structures that interact with light at wavelength size-scales.
"If we want to measure the light's full polarization state, we need to take several pictures along different polarization directions," said Noah Rubin, first author of the paper and graduate student in the Capasso Lab. "Previous devices either used moving parts or sent light along multiple paths to acquire the multiple images, resulting in bulky optics. A newer strategy uses specially patterned camera pixels, but this approach does not measure the full polarization state and requires a non-standard imaging sensor. In this work, we were able to take all of the optics needed and integrate them in a single, simple device with a metasurface."
Using a new understanding how polarized light interacts with objects, the researchers designed a metasurface that uses an array of subwavelength spaced nanopillars to direct light based on its polarization. The light then forms four images, each one showing a different aspect of the polarization. Taken together, these give a full snapshot of polarization at every pixel.
The device is about two centimeters in length and no more complicated than a camera on a smartphone. With an attached lens and protective case, the device is about the size of a small lunch box. The researchers tested the camera to show defects in injection-molded plastic objects, took it outside to film the polarization off car windshields and even took selfies to demonstrate how a polarization camera can visualize the 3D contours of a face.
"This technology could be integrated into existing imaging systems, such as the one in your cell phone or car, enabling the widespread adoption of polarization imaging and new applications previously unforeseen," said Rubin.
"This research opens an exciting new direction for camera technology with unprecedented compactness, allowing us to envision applications in atmospheric science, remote sensing, facial recognition, machine vision and more," said Capasso.
The Harvard Office of Technology Development has protected the intellectual property relating to this project and is exploring commercialization opportunities.
Read more at Science Daily
Technicolor forever changed how cameras -- and people -- saw and experienced the world around them. Today, there is a new precipice -- this one, offering views of a polarized world.
Polarization, the direction in which light vibrates, is invisible to the human eye (but visible to some species of shrimp and insects). But it provides a great deal of information about the objects with which it interacts. Cameras that see polarized light are currently used to detect material stress, enhance contrast for object detection, and analyze surface quality for dents or scratches.
However, like the early color cameras, current-generation polarization-sensitive cameras are bulky. Moreover, they often rely on moving parts and are costly, severely limiting the scope of their potential application.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a highly compact, portable camera that can image polarization in a single shot. The miniature camera -- about the size of a thumb -- could find a place in the vision systems of autonomous vehicles, onboard planes or satellites to study atmospheric chemistry, or be used to detect camouflaged objects.
The research is published in Science.
"This research is game-changing for imaging," said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper. "Most cameras can typically only detect the intensity and color of light but can't see polarization. This camera is a new eye on reality, allowing us to reveal how light is reflected and transmitted by the world around us."
"Polarization is a feature of light that is changed upon reflection off a surface," said Paul Chevalier, a postdoctoral fellow at SEAS and co-author of the study. "Based on that change, polarization can help us in the 3D reconstruction of an object, to estimate its depth, texture and shape, and to distinguish man-made objects from natural ones, even if they're the same shape and color."
To unlock that powerful world of polarization, Capasso and his team harnessed the potential of metasurfaces, nanoscale structures that interact with light at wavelength size-scales.
"If we want to measure the light's full polarization state, we need to take several pictures along different polarization directions," said Noah Rubin, first author of the paper and graduate student in the Capasso Lab. "Previous devices either used moving parts or sent light along multiple paths to acquire the multiple images, resulting in bulky optics. A newer strategy uses specially patterned camera pixels, but this approach does not measure the full polarization state and requires a non-standard imaging sensor. In this work, we were able to take all of the optics needed and integrate them in a single, simple device with a metasurface."
Using a new understanding how polarized light interacts with objects, the researchers designed a metasurface that uses an array of subwavelength spaced nanopillars to direct light based on its polarization. The light then forms four images, each one showing a different aspect of the polarization. Taken together, these give a full snapshot of polarization at every pixel.
The device is about two centimeters in length and no more complicated than a camera on a smartphone. With an attached lens and protective case, the device is about the size of a small lunch box. The researchers tested the camera to show defects in injection-molded plastic objects, took it outside to film the polarization off car windshields and even took selfies to demonstrate how a polarization camera can visualize the 3D contours of a face.
"This technology could be integrated into existing imaging systems, such as the one in your cell phone or car, enabling the widespread adoption of polarization imaging and new applications previously unforeseen," said Rubin.
"This research opens an exciting new direction for camera technology with unprecedented compactness, allowing us to envision applications in atmospheric science, remote sensing, facial recognition, machine vision and more," said Capasso.
The Harvard Office of Technology Development has protected the intellectual property relating to this project and is exploring commercialization opportunities.
Read more at Science Daily
Pain signaling in humans more rapid than previously known
Pain signals can travel as fast as touch signals, according to a new study from researchers at Linköping University in Sweden, Liverpool John Moores University in the UK, and the National Institutes of Health (NIH) in the US. The discovery of a rapid pain-signalling system challenges our current understanding of pain. The study is published in the scientific journal Science Advances.
It has until now been believed that nerve signals for pain are always conducted more slowly than those for touch. The latter signals, which allow us to determine where we are being touched, are conducted by nerves that have a fatty sheath of myelin that insulates the nerve. Nerves with a thick layer of myelin conduct signals more rapidly than unmyelinated nerves. In contrast, the signalling of pain in humans has been thought to be considerably slower and carried out by nerves that have only a thin layer of myelin, or none at all.
In monkeys and many other mammals, on the other hand, part of the pain-signalling system can conduct nerve signals just as fast as the system that signals touch. The scientists speculated whether such a system is also present in humans.
"The ability to feel pain is vital to our survival, so why should our pain-signalling system be so much slower than the system used for touch, and so much slower than it could be?" asks Saad Nagi, principal research engineer of the Department of Clinical and Experimental Medicine and the Center for Social and Affective Neuroscience (CSAN) at Linköping University.
To answer this, the scientists used a technique that allowed them to detect the signals in the nerve fibres from a single nerve cell. They examined 100 healthy volunteers and looked for nerve cells that conducted signals as rapidly as the nerve cells that detect touch, but that had the properties of pain receptors, otherwise known as nociceptors. Pain receptors are characterised by the ability to detect noxious stimuli, such as pinching and abrasion of the skin, while not reacting to light touch. The researchers found that 12% of thickly myelinated nerve cells had the same properties as pain receptors, and in these nerve cells the conduction speed was as high as in touch-sensitive nerve cells.
The next step of the scientists' research was to determine the function of these ultrafast pain receptors. By applying short electrical pulses through the measurement electrodes, they could stimulate individual nerve cells. The volunteers described that they experienced sharp or pinprick pain.
"When we activated an individual nerve cell, it caused a perception of pain, so we conclude that these nerve cells are connected to pain centres in the brain," says Saad Nagi.
The research team also investigated patients with various rare neurological conditions. One group of people had, as adults, acquired nerve damage that led to the thickly myelinated nerve fibres being destroyed, while the small fibres were spared. These patients cannot detect light touch. The scientists predicted that the loss of myelinated nerve fibres should also affect the rapidly conducting pain system they had identified. It turned out that these people had an impaired ability to experience mechanical pain. Examination of patients with two other rare neurological conditions gave similar results. These results may be highly significant for pain research, and for the diagnosis and care of patients with pain.
Read more at Science Daily
It has until now been believed that nerve signals for pain are always conducted more slowly than those for touch. The latter signals, which allow us to determine where we are being touched, are conducted by nerves that have a fatty sheath of myelin that insulates the nerve. Nerves with a thick layer of myelin conduct signals more rapidly than unmyelinated nerves. In contrast, the signalling of pain in humans has been thought to be considerably slower and carried out by nerves that have only a thin layer of myelin, or none at all.
In monkeys and many other mammals, on the other hand, part of the pain-signalling system can conduct nerve signals just as fast as the system that signals touch. The scientists speculated whether such a system is also present in humans.
"The ability to feel pain is vital to our survival, so why should our pain-signalling system be so much slower than the system used for touch, and so much slower than it could be?" asks Saad Nagi, principal research engineer of the Department of Clinical and Experimental Medicine and the Center for Social and Affective Neuroscience (CSAN) at Linköping University.
To answer this, the scientists used a technique that allowed them to detect the signals in the nerve fibres from a single nerve cell. They examined 100 healthy volunteers and looked for nerve cells that conducted signals as rapidly as the nerve cells that detect touch, but that had the properties of pain receptors, otherwise known as nociceptors. Pain receptors are characterised by the ability to detect noxious stimuli, such as pinching and abrasion of the skin, while not reacting to light touch. The researchers found that 12% of thickly myelinated nerve cells had the same properties as pain receptors, and in these nerve cells the conduction speed was as high as in touch-sensitive nerve cells.
The next step of the scientists' research was to determine the function of these ultrafast pain receptors. By applying short electrical pulses through the measurement electrodes, they could stimulate individual nerve cells. The volunteers described that they experienced sharp or pinprick pain.
"When we activated an individual nerve cell, it caused a perception of pain, so we conclude that these nerve cells are connected to pain centres in the brain," says Saad Nagi.
The research team also investigated patients with various rare neurological conditions. One group of people had, as adults, acquired nerve damage that led to the thickly myelinated nerve fibres being destroyed, while the small fibres were spared. These patients cannot detect light touch. The scientists predicted that the loss of myelinated nerve fibres should also affect the rapidly conducting pain system they had identified. It turned out that these people had an impaired ability to experience mechanical pain. Examination of patients with two other rare neurological conditions gave similar results. These results may be highly significant for pain research, and for the diagnosis and care of patients with pain.
Read more at Science Daily
Jul 4, 2019
Murder in the Paleolithic? Evidence of violence behind human skull remains
New analysis of the fossilized skull of an Upper Paleolithic man suggests that he died a violent death, according to a study published July 3, 2019 in the open-access journal PLOS ONE by an international team from Greece, Romania and Germany led by the Eberhard Karls Universität Tübingen, Germany.
The fossilized skull of a Paleolithic adult man, known as the Cioclovina calvaria, was originally uncovered in a cave in South Transylvania and is thought to be around 33,000 years old. Since its discovery, this fossil has been extensively studied. Here, the authors reassessed trauma on the skull -- specifically a large fracture on the right aspect of the cranium which has been disputed in the past -- in order to evaluate whether this specific fracture occurred at the time of death or as a postmortem event.
The authors conducted experimental trauma simulations using twelve synthetic bone spheres, testing scenarios such as falls from various heights as well as single or double blows from rocks or bats. Along with these simulations, the authors inspected the fossil both visually and virtually using computed tomography technology.
The authors found there were actually two injuries at or near the time of death: a linear fracture at the base of the skull, followed by a depressed fracture on the right side of the cranial vault. The simulations showed that these fractures strongly resemble the pattern of injury resulting from consecutive blows with a bat-like object; the positioning suggests the blow resulting in the depressed fracture came from a face-to-face confrontation, possibly with the bat in the perpetrator's left hand. The researchers' analysis indicates that the two injuries were not the result of accidental injury, post-mortem damage, or a fall alone.
While the fractures would have been fatal, only the fossilized skull has been found so it's possible that bodily injuries leading to death might also have been sustained. Regardless, the authors state that the forensic evidence described in this study points to an intentionally-caused violent death, suggesting that homicide was practiced by early humans during the Upper Paleolithic.
The authors add: "The Upper Paleolithic was a time of increasing cultural complexity and technological sophistication. Our work shows that violent interpersonal behaviour and murder was also part of the behavioural repertoire of these early modern Europeans."
From Science Daily
The fossilized skull of a Paleolithic adult man, known as the Cioclovina calvaria, was originally uncovered in a cave in South Transylvania and is thought to be around 33,000 years old. Since its discovery, this fossil has been extensively studied. Here, the authors reassessed trauma on the skull -- specifically a large fracture on the right aspect of the cranium which has been disputed in the past -- in order to evaluate whether this specific fracture occurred at the time of death or as a postmortem event.
The authors conducted experimental trauma simulations using twelve synthetic bone spheres, testing scenarios such as falls from various heights as well as single or double blows from rocks or bats. Along with these simulations, the authors inspected the fossil both visually and virtually using computed tomography technology.
The authors found there were actually two injuries at or near the time of death: a linear fracture at the base of the skull, followed by a depressed fracture on the right side of the cranial vault. The simulations showed that these fractures strongly resemble the pattern of injury resulting from consecutive blows with a bat-like object; the positioning suggests the blow resulting in the depressed fracture came from a face-to-face confrontation, possibly with the bat in the perpetrator's left hand. The researchers' analysis indicates that the two injuries were not the result of accidental injury, post-mortem damage, or a fall alone.
While the fractures would have been fatal, only the fossilized skull has been found so it's possible that bodily injuries leading to death might also have been sustained. Regardless, the authors state that the forensic evidence described in this study points to an intentionally-caused violent death, suggesting that homicide was practiced by early humans during the Upper Paleolithic.
The authors add: "The Upper Paleolithic was a time of increasing cultural complexity and technological sophistication. Our work shows that violent interpersonal behaviour and murder was also part of the behavioural repertoire of these early modern Europeans."
From Science Daily
Winter monsoons became stronger during geomagnetic reversal
New evidence suggests that high-energy particles from space known as galactic cosmic rays affect the Earth's climate by increasing cloud cover, causing an "umbrella effect."
When galactic cosmic rays increased during the Earth's last geomagnetic reversal transition 780,000 years ago, the umbrella effect of low-cloud cover led to high atmospheric pressure in Siberia, causing the East Asian winter monsoon to become stronger. This is evidence that galactic cosmic rays influence changes in the Earth's climate. The findings were made by a research team led by Professor Masayuki Hyodo (Research Center for Inland Seas, Kobe University) and published on June 28 in the online edition of Scientific Reports.
The Svensmark Effect is a hypothesis that galactic cosmic rays induce low cloud formation and influence the Earth's climate. Tests based on recent meteorological observation data only show minute changes in the amounts of galactic cosmic rays and cloud cover, making it hard to prove this theory. However, during the last geomagnetic reversal transition, when the amount of galactic cosmic rays increased dramatically, there was also a large increase in cloud cover, so it should be possible to detect the impact of cosmic rays on climate at a higher sensitivity.
In the Chinese Loess Plateau, just south of the Gobi Desert near the border of Mongolia, dust has been transported for 2.6 million years to form loess layers -- sediment created by the accumulation of wind-blown silt -- that can reach up to 200 meters in thickness. If the wind gets stronger, the coarse particles are carried further, and larger amounts are transported. Focusing on this phenomenon, the research team proposed that winter monsoons became stronger under the umbrella effect of increased cloud cover during the geomagnetic reversal. They investigated changes in particle size and accumulation speed of loess layer dust in two Loess Plateau locations.
In both locations, for about 5000 years during the geomagnetic reversal 780,000 years ago, they discovered evidence of stronger winter monsoons: particles became coarser, and accumulation speeds were up to > 3 times faster. These strong winter monsoons coincide with the period during the geomagnetic reversal when the Earth's magnetic strength fell to less than ¼, and galactic cosmic rays increased by over 50%. This suggests that the increase in cosmic rays was accompanied by an increase in low-cloud cover, the umbrella effect of the clouds cooled the continent, and Siberian high atmospheric pressure became stronger. Added to other phenomena during the geomagnetic reversal -- evidence of an annual average temperature drop of 2-3 degrees Celsius, and an increase in annual temperature ranges from the sediment in Osaka Bay -- this new discovery about winter monsoons provides further proof that the climate changes are caused by the cloud umbrella effect.
Read more at Science Daily
When galactic cosmic rays increased during the Earth's last geomagnetic reversal transition 780,000 years ago, the umbrella effect of low-cloud cover led to high atmospheric pressure in Siberia, causing the East Asian winter monsoon to become stronger. This is evidence that galactic cosmic rays influence changes in the Earth's climate. The findings were made by a research team led by Professor Masayuki Hyodo (Research Center for Inland Seas, Kobe University) and published on June 28 in the online edition of Scientific Reports.
The Svensmark Effect is a hypothesis that galactic cosmic rays induce low cloud formation and influence the Earth's climate. Tests based on recent meteorological observation data only show minute changes in the amounts of galactic cosmic rays and cloud cover, making it hard to prove this theory. However, during the last geomagnetic reversal transition, when the amount of galactic cosmic rays increased dramatically, there was also a large increase in cloud cover, so it should be possible to detect the impact of cosmic rays on climate at a higher sensitivity.
In the Chinese Loess Plateau, just south of the Gobi Desert near the border of Mongolia, dust has been transported for 2.6 million years to form loess layers -- sediment created by the accumulation of wind-blown silt -- that can reach up to 200 meters in thickness. If the wind gets stronger, the coarse particles are carried further, and larger amounts are transported. Focusing on this phenomenon, the research team proposed that winter monsoons became stronger under the umbrella effect of increased cloud cover during the geomagnetic reversal. They investigated changes in particle size and accumulation speed of loess layer dust in two Loess Plateau locations.
In both locations, for about 5000 years during the geomagnetic reversal 780,000 years ago, they discovered evidence of stronger winter monsoons: particles became coarser, and accumulation speeds were up to > 3 times faster. These strong winter monsoons coincide with the period during the geomagnetic reversal when the Earth's magnetic strength fell to less than ¼, and galactic cosmic rays increased by over 50%. This suggests that the increase in cosmic rays was accompanied by an increase in low-cloud cover, the umbrella effect of the clouds cooled the continent, and Siberian high atmospheric pressure became stronger. Added to other phenomena during the geomagnetic reversal -- evidence of an annual average temperature drop of 2-3 degrees Celsius, and an increase in annual temperature ranges from the sediment in Osaka Bay -- this new discovery about winter monsoons provides further proof that the climate changes are caused by the cloud umbrella effect.
Read more at Science Daily
Measuring the laws of nature
There are some numerical values that define the basic properties of our universe. They are just as they are, and no one can tell why. These include, for example, the value of the speed of light, the mass of the electron, or the coupling constants that define the strength of the forces of nature.
One of these coupling constants, the "weak axial vector coupling constant" (abbreviated to gA), has now been measured with very high precision. This constant is needed to explain nuclear fusion in the sun, to understand the formation of elements shortly after the Big Bang, or to understand important experiments in particle physics. With the help of sophisticated neutron experiments, the value of the coupling constant gA has now been determined with an accuracy of 0.04 % The result has now been published in the journal "Physical Review Letters."
When particles change
There are four fundamental forces in our universe: electromagnetism, strong and weak nuclear force, and gravity. "To calculate these forces, we have to know certain parameters that determine their strength -- and especially in the case of weak interaction, this is a complicated matter," says Prof. Hartmut Abele from the Institute of Atomic and Subatomic Physics at TU Wien (Vienna). Weak interaction plays a crucial role when certain particles are transformed into others -- for example, when two protons merge into a nucleus in the sun and one of them becomes a neutron. To analyze such processes, the "weak axial vector coupling constant" gA has to be known.
There have been different attempts to measure gA. "For some of them, however, systematic corrections were required. Major disturbing factors can change the result by up to 30%," says Hartmut Abele.
A different measuring principle called "PERKEO" was developed in the 1980s in Heidelberg by Prof. Dirk Dubbers. Hartmut Abele has been involved in the work on the PERKEO detectors for many years, he himself has developed "PERKEO 2" as part of his dissertation. He works together with his former student Prof. Bastian Märkisch from TU Munich and Torsten Soldner from the Institut Laue-Langevin in Grenoble to significantly improve the measurement. With "PERKEO 3," new measurements have now been carried out in Grenoble, far exceeding all previous experiments in terms of accuracy.
The PEREKO detector analyzes neutrons, which decay into protons and emit a neutrino and an electron. "This electron emission is not perfectly symmetric," explains Hartmut Abele. "On one side, a few more electrons are emitted than on the other -- that depends on the spin direction of the neutron." The PERKEO detector uses strong magnetic fields to collect the electrons in both directions and then counts them. From the strength of the asymmetry, i.e. the difference in the number of electrons in the two directions, one can then directly deduce the value of the coupling constant gA.
Read more at Science Daily
One of these coupling constants, the "weak axial vector coupling constant" (abbreviated to gA), has now been measured with very high precision. This constant is needed to explain nuclear fusion in the sun, to understand the formation of elements shortly after the Big Bang, or to understand important experiments in particle physics. With the help of sophisticated neutron experiments, the value of the coupling constant gA has now been determined with an accuracy of 0.04 % The result has now been published in the journal "Physical Review Letters."
When particles change
There are four fundamental forces in our universe: electromagnetism, strong and weak nuclear force, and gravity. "To calculate these forces, we have to know certain parameters that determine their strength -- and especially in the case of weak interaction, this is a complicated matter," says Prof. Hartmut Abele from the Institute of Atomic and Subatomic Physics at TU Wien (Vienna). Weak interaction plays a crucial role when certain particles are transformed into others -- for example, when two protons merge into a nucleus in the sun and one of them becomes a neutron. To analyze such processes, the "weak axial vector coupling constant" gA has to be known.
There have been different attempts to measure gA. "For some of them, however, systematic corrections were required. Major disturbing factors can change the result by up to 30%," says Hartmut Abele.
A different measuring principle called "PERKEO" was developed in the 1980s in Heidelberg by Prof. Dirk Dubbers. Hartmut Abele has been involved in the work on the PERKEO detectors for many years, he himself has developed "PERKEO 2" as part of his dissertation. He works together with his former student Prof. Bastian Märkisch from TU Munich and Torsten Soldner from the Institut Laue-Langevin in Grenoble to significantly improve the measurement. With "PERKEO 3," new measurements have now been carried out in Grenoble, far exceeding all previous experiments in terms of accuracy.
The PEREKO detector analyzes neutrons, which decay into protons and emit a neutrino and an electron. "This electron emission is not perfectly symmetric," explains Hartmut Abele. "On one side, a few more electrons are emitted than on the other -- that depends on the spin direction of the neutron." The PERKEO detector uses strong magnetic fields to collect the electrons in both directions and then counts them. From the strength of the asymmetry, i.e. the difference in the number of electrons in the two directions, one can then directly deduce the value of the coupling constant gA.
Read more at Science Daily
Scientists weigh the balance of matter in galaxy clusters
A method of weighing the quantities of matter in galaxy clusters -- the largest objects in our universe -- has shown a balance between the amounts of hot gas, stars and other materials.
The results are the first to use observational data to measure this balance, which was theorized 20 years ago, and will yield fresh insight into the relationship between ordinary matter that emits light and dark matter, and about how our universe is expanding.
Galaxy clusters are the largest objects in the universe, each composed of around 1,000 massive galaxies. They contain vast amounts of dark matter, along with hot gas and cooler "ordinary matter," such as stars and cooler gas.
In a new study, published in Nature Communications, an international team led by astrophysicists from the University of Michigan in the US and the University of Birmingham in the UK used data from the Local Cluster Substructure Survey (LoCuSS) to measure the connections between the three main mass components that comprise galaxy clusters -- dark matter, hot gas, and stars.
Members of the research team had spent 12 years gathering data, which span a factor of 10 million in wavelength, using the Chandra and XMM-Newton satellites, the ROSAT All-sky survey, Subaru telescope, United Kingdom Infrared Telescope (UKIRT), Mayall telecope, the Sunyaev Zeldovich Array, and the Planck satellite. Using sophisticated statistical models and algorithms built by Dr Arya Farahi during his doctoral studies at the University of Michigan the team was able to conclude that the sum of gas and stars across the clusters that they studied is a nearly fixed fraction of the dark matter mass. This means that as stars form, the amount of hot gas available will decrease proportionally
"This validates the predictions of the prevailing cold dark matter theory. Everything is consistent with our current understanding of the universe," said Dr Farahi, currently a McWilliams Postdoctoral Fellow in the Department of Physics at Carnegie Mellon University.
Dr Graham Smith of the School of Physics and Astronomy at the University of Birmingham and Principal Investigator of LoCuSS, says: "A certain amount of material within the universe collapses to form galaxy clusters.
"But once they are formed, these clusters are 'closed boxes'. The hot gas has either formed stars, or still remains as gas, but the overall quantity remains constant."
"This research is powered by more than a decade of telescope investments," adds Professor August E. Evrard, of the University of Michigan. "Using this high quality data, we were able to characterise 41 nearby galaxy clusters and find a special relationship, specifically anti-correlated behaviour between the mass in stars and the mass in hot gas. This is significant because these two measurements together give us the best indication of the total system mass."
The findings will be crucial to astronomers' efforts to measure the properties of the universe as a whole. By gaining a better understanding of the internal physics of galaxy clusters, researchers will be able to better understand the behaviour of dark energy and the processes behind the expansion of the universe.
"Galaxy clusters are intrinsically fascinating, but in many ways still mysterious objects," adds Dr Smith. "Unpicking the complex astrophysics governing these objects will open many doors onto a broader understanding of the universe. Essentially, if we want to be able to claim that we understand how the universe works, we need to understand galaxy clusters."
Data of the kind studied by the team will grow by several orders of magnitude over the coming decades thanks to next-generation telescopes such as the Large Synoptic Survey Telescope (LSST) which is currently under construction in Chile, and e-ROSITA, a new x-ray satellite. Both will begin observations in the early 2020s.
Read more at Science Daily
The results are the first to use observational data to measure this balance, which was theorized 20 years ago, and will yield fresh insight into the relationship between ordinary matter that emits light and dark matter, and about how our universe is expanding.
Galaxy clusters are the largest objects in the universe, each composed of around 1,000 massive galaxies. They contain vast amounts of dark matter, along with hot gas and cooler "ordinary matter," such as stars and cooler gas.
In a new study, published in Nature Communications, an international team led by astrophysicists from the University of Michigan in the US and the University of Birmingham in the UK used data from the Local Cluster Substructure Survey (LoCuSS) to measure the connections between the three main mass components that comprise galaxy clusters -- dark matter, hot gas, and stars.
Members of the research team had spent 12 years gathering data, which span a factor of 10 million in wavelength, using the Chandra and XMM-Newton satellites, the ROSAT All-sky survey, Subaru telescope, United Kingdom Infrared Telescope (UKIRT), Mayall telecope, the Sunyaev Zeldovich Array, and the Planck satellite. Using sophisticated statistical models and algorithms built by Dr Arya Farahi during his doctoral studies at the University of Michigan the team was able to conclude that the sum of gas and stars across the clusters that they studied is a nearly fixed fraction of the dark matter mass. This means that as stars form, the amount of hot gas available will decrease proportionally
"This validates the predictions of the prevailing cold dark matter theory. Everything is consistent with our current understanding of the universe," said Dr Farahi, currently a McWilliams Postdoctoral Fellow in the Department of Physics at Carnegie Mellon University.
Dr Graham Smith of the School of Physics and Astronomy at the University of Birmingham and Principal Investigator of LoCuSS, says: "A certain amount of material within the universe collapses to form galaxy clusters.
"But once they are formed, these clusters are 'closed boxes'. The hot gas has either formed stars, or still remains as gas, but the overall quantity remains constant."
"This research is powered by more than a decade of telescope investments," adds Professor August E. Evrard, of the University of Michigan. "Using this high quality data, we were able to characterise 41 nearby galaxy clusters and find a special relationship, specifically anti-correlated behaviour between the mass in stars and the mass in hot gas. This is significant because these two measurements together give us the best indication of the total system mass."
The findings will be crucial to astronomers' efforts to measure the properties of the universe as a whole. By gaining a better understanding of the internal physics of galaxy clusters, researchers will be able to better understand the behaviour of dark energy and the processes behind the expansion of the universe.
"Galaxy clusters are intrinsically fascinating, but in many ways still mysterious objects," adds Dr Smith. "Unpicking the complex astrophysics governing these objects will open many doors onto a broader understanding of the universe. Essentially, if we want to be able to claim that we understand how the universe works, we need to understand galaxy clusters."
Data of the kind studied by the team will grow by several orders of magnitude over the coming decades thanks to next-generation telescopes such as the Large Synoptic Survey Telescope (LSST) which is currently under construction in Chile, and e-ROSITA, a new x-ray satellite. Both will begin observations in the early 2020s.
Read more at Science Daily
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