Heavens

An infinite chain of hydrogen atoms is just about the simplest bulk material imaginable — a never-ending single-file line of protons surrounded by electrons. Yet a new computational study combining four cutting-edge methods finds that the modest material boasts fantastic and surprising quantum properties.

By computing the consequences of changing the spacing between the atoms, an international team of researchers from the Flatiron Institute and the Simons Collaboration on the Many Electron Problem found that the hydrogen chain’s properties can be varied in unexpected and drastic ways. That includes the chain transforming from a magnetic insulator into a metal, the researchers report September 14 in Physical Review X.

The computational methods used in the study present a significant step toward custom-designing materials with sought-after properties, such as the possibility of high-temperature superconductivity in which electrons flow freely through a material without losing energy, says the study’s senior author Shiwei Zhang. Zhang is a senior research scientist at the Center for Computational Quantum Physics (CCQ) at the Simons Foundation’s Flatiron Institute in New York City.

“The main purpose was to apply our tools to a realistic situation,” Zhang says. “Almost as a side product, we discovered all of this interesting physics of the hydrogen chain. We didn’t think that it would be as rich as it turned out to be.”

Zhang, who is also a chancellor professor of physics at the College of William and Mary, co-led the research with Mario Motta of IBM Quantum. Motta serves as first author of the paper alongside Claudio Genovese of the International School for Advanced Studies (SISSA) in Italy, Fengjie Ma of Beijing Normal University, Zhi-Hao Cui of the California Institute of Technology, and Randy Sawaya of the University of California, Irvine. Additional co-authors include CCQ co-director Andrew Millis, CCQ Flatiron Research Fellow Hao Shi and CCQ research scientist Miles Stoudenmire.

The paper’s long author list — 17 co-authors in total — is uncommon for the field, Zhang says. Methods are often developed within individual research groups. The new study brings many methods and research groups together to combine forces and tackle a particularly thorny problem. “The next step in the field is to move toward more realistic problems,” says Zhang, “and there is no shortage of these problems that require collaboration.”

While conventional methods can explain the properties of some materials, other materials, such as infinite hydrogen chains, pose a more daunting computational hurdle. That’s because the behavior of the electrons in those materials is heavily influenced by interactions between electrons. As electrons interact, they become quantum-mechanically entangled with one another. Once entangled, the electrons can no longer be treated individually, even when they are physically separate.

The sheer number of electrons in a bulk material — roughly 100 billion trillion per gram — means that conventional brute force methods can’t even come close to providing a solution. The number of electrons is so large that it’s practically infinite when thinking at the quantum scale.

Thankfully, quantum physicists have developed clever methods of tackling this many-electron problem. The new study combines four such methods: variational Monte Carlo, lattice-regularized diffusion Monte Carlo, auxiliary-field quantum Monte Carlo, and standard and sliced-basis density-matrix renormalization group. Each of these cutting-edge methods has its strengths and weaknesses. Using them in parallel and in concert provides a fuller picture, Zhang says.

Researchers, including authors of the new study, previously used those methods in 2017 to compute the amount of energy each atom in a hydrogen chain has as a function of the chain’s spacing. This computation, known as the equation of state, doesn’t provide a complete picture of the chain’s properties. By further honing their methods, the researchers did just that.

At large separations, the researchers found that the electrons remain confined to their respective protons. Even at such large distances, the electrons still ‘know’ about each other and become entangled. Because the electrons can’t hop from atom to atom as easily, the chain acts as an electrical insulator.

As the atoms move closer together, the electrons try to form molecules of two hydrogen atoms each. Because the protons are fixed in place, these molecules can’t form. Instead, the electrons ‘wave’ to one another, as Zhang puts it. Electrons will lean toward an adjacent atom. In this phase, if you find an electron leaning toward one of its neighbors, you’ll find that neighboring electron responding in return. This pattern of pairs of electrons leaning toward each other will continue in both directions.

Moving the hydrogen atoms even closer together, the researchers discovered that the hydrogen chain transformed from an insulator into a metal with electrons moving freely between atoms. Under a simple model of interacting particles known as the one-dimensional Hubbard model, this transition shouldn’t happen, as electrons should electrically repel each other enough to restrict movement. In the 1960s, British physicist Nevill Mott predicted the existence of an insulator-to-metal transition based on a mechanism involving so-called excitons, each consisting of an electron trying to break free of its atom and the hole it leaves behind. Mott proposed an abrupt transition driven by the breakup of these excitons — something the new hydrogen chain study didn’t see.

Instead, the researchers discovered a more nuanced insulator-to-metal transition. As the atoms move closer together, electrons gradually get peeled off the tightly bound inner core around the proton line and become a thin `vapor’ only loosely bound to the line and displaying interesting magnetic structures.

The infinite hydrogen chain will be a key benchmark in the future in the development of computational methods, Zhang says. Scientists can model the chain using their methods and check their results for accuracy and efficiency against the new study.

The new work is a leap forward in the quest to utilize computational methods to model realistic materials, the researchers say. In the 1960s, British physicist Neil Ashcroft proposed that metallic hydrogen, for instance, might be a high-temperature superconductor. While the one-dimensional hydrogen chain doesn’t exist in nature (it would crumple into a three-dimensional structure), the researchers say that the lessons they learned are a crucial step forward in the development of the methods and physical understanding needed to tackle even more realistic materials.

Journal

Physical Review X

DOI

10.1103/PhysRevX.10.031058

A new study by Rutgers University researchers finds that job candidates with disabilities are more likely to make a positive first impression on prospective employers when they promote technical skills rather than soft skills, such as their ability to lead others.

The findings, published in the International Journal of Conflict Management, contrast this with the results for candidates without disabilities who were positively evaluated when they highlighted either hard or soft skills during initial job interviews.

"Job interviews are challenging for everyone, but particularly so for people with disabilities who have always had difficulties presenting themselves favorably to gain employment," said Rutgers Business School professor Mason Ameri.

"People with disabilities encounter an implicit bias that they will not be as productive as their non-disabled peers," said Ameri, who co-authored the study. "Knowing how to navigate the conversation with potential employers is critical for leveling the playing field."

In three studies, 1,711 participants watched videos of candidates - either visibly seated in a wheelchair or not - using influence tactics to answer an opening question during an interview for a project manager position. Participants were asked to rate their perceptions of the job candidate's employability and appropriate level of salary, as well as how trustworthy they appeared.

Among the findings:

Employability: For candidates without disabilities, discussion of hard skills or soft skills led to more favorable perceptions. While the expression of hard skills similarly improved the employability rating of the candidate with the disability, discussion of soft skills did not.

Pay: When candidates with disabilities discussed salary early in the job interview, it appeared to hurt them more than when candidates without disabilities raised the same topic. Still, even for candidates without disabilities, announcing a salary figure so early in the process seemed to be off-putting in terms of whether they should get the job at all.

Trustworthiness: Candidates with disabilities were not viewed as trustworthy regardless of the tactic they used. For candidates without disabilities, ratings of trustworthiness increased when they discussed hard or soft skills. However, other tactics such as signaling alternative offers or suggesting a salary figure did not have the same positive effect.

"Influence tactics such as emphasizing your skills and abilities are a good idea but don't necessarily work the same way for everyone," said Terri Kurtzberg, co-author and professor at Rutgers Business School. "Instead, people with disabilities should focus on job-related hard skills and competencies instead of softer skills and warmth. This choice accelerated positive impressions of employability."

Owing to their astonishing and versatile properties, atomically thin monolayer and bilayer forms of semiconducting transition metal dichalcogenides have aroused great interest in recent years. Most attention has so far been paid to the optical properties of these materials, such as molybdenum sulfide (MoS) and tungsten diselenide (WSe2). These compounds show great promise as nanoscale elements for applications in opto-electronic and quantum technologies. In a new study, LMU physicists led by Alexander Högele have now developed a theoretical model, which describes the effects of magnetic fields on the behavior of 'excitons' in two-dimensional ultrathin transition metal dichalcogenides. Excitons are strongly bound 'quasiparticles', composed of an electron in the conduction band and its positively charged counterpart in the valence band referred to as a 'hole'. In the presence of strong magnetic fields, the energy states of such quasiparticles (i.e. the frequencies at which they emit and absorb light) split up. This spectral splitting can be experimentally measured and - more importantly in the present context - it can also be theoretically predicted.

In the new study, the team cooled monolayer and bilayer samples of WSe2 to the temperature of liquid helium of a few degrees Kelvin. The researchers then used optical spectroscopy to measure the emission spectra as a fucntion of magnetic field up to 9 Tesla and determined the field-induced splitting. "Measurements like this are useful to study excitons, which in turn determine the light-matter interaction of semiconductors", Högele explains.

It was already known that excitons can form in different configurations. In addition to bright excitons, which couple directly to light, the pairing of electrons and holes can produce 'spin-dark' and 'momentum-dark' excitons. Up to now, it has not been possible to conclusively assign the signatures observed in emission spectra to these different exciton species. In the presence of magnetic field, however, individual emission peaks exhibit characteristic spectral splittings. "This splitting can be used to discriminate between the various types of excitons," says Högele, "but only if we have the according theoretical model." The LMU team developed theory to calculate from first principles the spectral splitting for the different types of excitons in monolayer and bilayer WSe2 subjected to magnetic field, and compared their theoretical predictions with the experimental data.

The results provide a better understanding of the opto-electronic properties of WSe2 and related transition-metal dichalcogenides where excitons represent the primary interface for light to interact with nanoscale matter. Ultrathin layers of WSe2 serve as a testbed for technological exploitations of light-matter coupling in opto-electronic devices including photodetectors and emitters or photovoltaic devices. "These ultrathin materials are mechanically flexible and extremely compact", says Högele. They are also potentially viable for quantum technologies as they host 'valleys' as quantum degrees of freedom that can serve as qubits, the basic units of information processing in quantum computers.

The "IceCube" neutrino observatory deep in the ice of the South Pole has already brought spectacular new insights into cosmic incidents of extremely high energies. In order to investigate the cosmic origins of elementary particles with even higher energies, Prof. Elisa Resconi from the Technical University of Munich (TUM) has now started an international initiative to build a neutrino telescope several cubic kilometers in size in the northeastern Pacific.

Astronomers observe the light that comes to us from distant celestial objects to explore the Universe. However, light does not tell us much about the highest energy events beyond our Galaxy, such as the jets of active galactic nuclei, gamma-ray bursts or supernovae, because photons in the upper gamma-ray range lose their extreme energies on their long way through the Universe through interaction with other particles.

Just like light, neutrinos traverse space at the speed of light (almost) but interact extremely rarely with other particles. They maintain their energy and direction, which makes them unique messengers of the highest energy universe.

Messenger of distant cosmic events

Since 2013, when the IceCube Neutrino Observatory detected extragalactic neutrinos for the first time, astrophysicists have been striving to understand from which cosmic sources they come and which physical mechanism has accelerated them to such extreme energies.

However, to solve the puzzle, more detectors with even larger volumes than that of the cubic-kilometre sized IceCube Observatory are required. Because neutrinos cannot be observed directly, only through Cherenkov radiation, the detectors must be located in ice or in water.

Initiative for a new neutrino telescope in the Pacific

Prof. Elisa Resconi, spokesperson of the Collaborative Research Center 1258 and Liesel-Beckmann Chair for Experimental Physics with Cosmic Particles at TUM, has now started an international initiative for a new neutrino telescope located in the Pacific Ocean off the coast of Canada: the Pacific Ocean Neutrino Experiment (P-ONE).

For that purpose, Resconi has partnered with a facility of the University of Victoria, Ocean Networks Canada (ONC), one of the world's largest and most advanced cabled ocean observatories.

Ideal conditions for a neutrino observatory

The ONC network node in the Cascadia basin at a depth of 2660 meters was selected for P-ONE. The extensive abyssal plain offers ideal conditions for a neutrino observatory spanning several cubic kilometres.

In summer 2018, ONC anchored a first pathfinder experiment in the Cascadia basin: the STRAW (Strings for Absorption length in water) experiment, two 140-meter-long strings equipped with light emitters and sensors to determine the attenuation of light in the ocean water, a parameter crucial for the design of P-ONE. In September 2020, STRAW-b will be installed, a 500 m steel cable with additional detectors. Both experiments were developed and built by Resconi's research group at the TUM Physics Department.

Next steps in 2023/24

The first segment of P-ONE, the Pacific Ocean Neutrino Explorer, a ring with seven 1000-meter-long strings with 20 detectors each, is planned to be installed in ONC's marine operation season in 2023/24 in collaboration with various Canadian universities.

"Astrophysical neutrinos have unlocked new potential for significantly advancing our knowledge of the extreme universe," says Darren Grant, professor at the Michigan State University (USA), and spokesperson of the IceCube collaboration. "P-ONE represents a unique opportunity to demonstrate large-scale neutrino detector deployment in the deep ocean, a critical step towards reaching the goal of a globally connected neutrino observatory that would provide peak all-sky sensitivity to these ideal cosmic messengers."

Elisa Resconi anticipates P-ONE with its seven segments to be completed by the end of the decade. "The experiment will then be perfectly equipped to uncover the provenance of the extragalactic neutrinos," says Resconi, "but what's more, high-energy neutrinos also hold the potential to reveal the nature of dark matter."

The P-ONE project includes the Technical University of Munich (Germany), University of Victoria and Ocean Networks Canada, University of Alberta, Queen's University, Simon Fraser University (all Canada), Michigan State University (USA), European Southern Observatory, Goethe University Frankfurt, GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, and Max Planck Institute for Physics (all Germany).

The project receives support from Ocean Networks Canada, an initiative of the University of Victoria funded in part by the Canada Foundation for Innovation. This work is funded by the German Research Foundation (DFG) through grant SFB 1258 "Neutrinos and Dark Matter in Astro- and Particle Physics" and the cluster of excellence "Origin and Structure of the Universe".

A special feature of the modules: They contain works of art by young international artists who create a connection between the earth and the deep sea and thus turn the pathfinder experiment into a unique underwater exhibition.

(SACRAMENTO, Calif.) -- People who own guns and those living with gun owners are substantially less worried about the risk of firearm injuries than individuals living in homes without guns, says a new study by violence prevention experts at UC Davis Health.

The research team said that with the rise in gun purchases during the COVID-19 pandemic, this difference in concern about the risks of gun violence provides an important opportunity for better public health messaging.

The study, titled "Firearm ownership and perceived risk of personal firearm injury," appeared online Sept. 3 in the British Medical Journal publication Injury Prevention.

The researchers noted that individuals' perceptions of firearm dangers are in sharp contrast to evidence showing that those with access to firearms are more likely to die from firearm violence, including suicide, homicide and unintentional injury, compared to those without access to guns.

"People usually say they purchase firearms for self-protection," said Julia Schleimer, lead author of the study and an epidemiologist with the UC Davis Violence Prevention Research Program (VPRP). "However, homicides from gunshots in the home are much more often criminal than self-defensive, and the risks of murder associated with firearm ownership are greater for women than for men."

Schleimer said this disconnect in awareness among gun owners and people living with gun owners about the actual dangers of firearm injury deserves more attention. She and her research colleagues suggest that more effective communications strategies could be developed to help improve firearm safety in the same way public health messaging about smoking, seatbelt use, and diet has reduced disease and injury.

The new study was based on data from respondents to the 2018 California Safety and Wellbeing Survey, which included the question, "In general, how worried are you about gun violence happening to you?"

The researchers found that about 58% of respondents reported being somewhat worried or very worried about gun violence happening to them. Yet, firearm owners were 60% less likely to be worried about gun violence happening to them, compared to non-firearm owners living in households without firearms. People living in households with gun owners were 46% less likely to be concerned about gun violence.

The study also identified people who were younger, female and non-white as feeling at greater risk of personal firearm injury.

"Firearm violence prevention programs should consider communications strategies rooted in the cultural contexts," said Schleimer. "In other words, to be effective, the messenger is as important as the message. This is important when informing gun owners and people living in households with guns about the risks associated with having a firearm in the home."

Firearm sales during crisis

Firearms are commonly owned for self-protection, and gun sales have surged in the U.S. amid the COVID-19 pandemic. Many Americans are experiencing increased anxiety, financial strain and disruptions to daily routines, including social distancing measures and stay-at-home orders. These factors, in combination with easy access to firearms, may increase unintentional shootings, suicides and intimate partner homicides, said the research team. In fact, most firearm deaths are suicides, not assaults.

"We need to understand the complexity of the people's perception of their risk for gun violence," said Garen Wintemute, director of the UC Davis Violence Prevention Research Program and a co-author of the study. "This is particularly important during times of crisis, when the perceived need for safety increases significantly."

New Rochelle, NY, September 8, 2020—Nearly 16% of LGBT adults in California own a gun or live in a household with a gun. These study results appear in the peer-reviewed journal Violence and Gender. Click here to read the article now.

“Efforts to prevent firearm injury, particularly among LGBT owners, will likely need to address suicide risk associated with ownership and self-protection as a primary driver of ownership,” state the researchers from University of California, Davis. 

The study presents the number and types of firearms owned, carrying behaviors, reasons for ownership, and means of acquisition for a sample of LGBT adults in California. 

"During this pandemic, firearm violence including suicide has increased along with the purchase of firearms. It is critical that we have a better understanding of firearm ownership practices among our LGBT communities, who report owning and carrying firearms for their own protection. According to this unique, critical California study, lesbian, gay, bisexual and transgender adults report having a firearm in their home, or carrying a firearm, for their own protection. This increases the likelihood of their own victimization including suicide. The findings of this California study serve to emphasize the importance of developing unique gun violence prevention strategies. These should include risk assessments specifically for the LGBT community in view of their firearm ownership practices and reasons for owning a firearm," says Editor-in-Chief Mary Ellen O'Toole, PhD, Forensic Behavioral Consultant and Senior FBI Profiler/Supervisory Special Agent (ret.) and currently, Director of the Forensic Sciences Program, George Mason University, Fairfax, VA.

About the Journal
Violence and Gender is the only peer-reviewed journal focusing on the understanding, prediction, and prevention of acts of violence. Through research papers, roundtable discussions, case studies, and other original content, the Journal critically examines biological, genetic, behavioral, psychological, racial, ethnic, and cultural factors as they relate to the gender of perpetrators of violence. Led by Editor-in-Chief Mary Ellen O'Toole, PhD, Forensic Behavioral Consultant and Senior FBI Profiler/Criminal Investigative Analyst (ret.), Violence and Gender explores the difficult issues that are vital to threat assessment and prevention of the epidemic of violence. Violence and Gender is published quarterly online with Open Access options and in print, and is the official journal of The Avielle Foundation. Complete tables of content and a sample issue may be viewed on the Violence and Gender website.

About the Publisher
Mary Ann Liebert, Inc., publishers is known for establishing authoritative peer-reviewed journals in many promising areas of science and biomedical research. A complete list of the firm's 90 journals, books, and newsmagazines is available on Mary Ann Liebert, Inc., publishers website.

Journal

Violence and Gender

DOI

10.1089/vio.2020.0024

New studies of a rare type of meteorite show that material from close to the Sun reached the outer solar system even as the planet Jupiter cleared a gap in the disk of dust and gas from which the planets formed. The results, published this week in Proceedings of the National Academy of Sciences, add to an emerging understanding of how our Solar System formed and how planets form around other stars.

The consensus theory on how planets form is that they accrete from a disk of dust and gas that rotates around a new-formed star. Evidence for the composition of this protoplanetary disk in our own solar system comes from chondrites, a type of meteorite made up of smaller particles, or chondrules, that collected together like a cosmic dust bunny.

"If we understand transport, we can understand the properties of the disk and infer how the planets were built," said Qingzhu Yin, professor of earth and planetary sciences at the University of California, Davis and coauthor on the paper.

The material in chondrites is extremely old, representing leftover dust and debris that from the very early solar system. Further evidence comes from rocks from the Earth and Moon and samples of cosmic dust and comet material collected by the Stardust mission and other space probes.

Researchers can work out approximately where and when these meteorites formed by measuring the ratios of isotopes of elements such as oxygen, titanium and chromium within them.

Previous work by Yin's laboratory and others showed that meteorites fall into two broad groups by composition. Carbonaceous meteorites are thought to have originated in the outer solar system. Non-carbonaceous meteorites formed from the disk closer to the sun where carbon-based and other volatile compounds were baked away.

Why was there not more mixing, if all the planets formed from the same protoplanetary disk? The explanation is that as Jupiter formed earlier, it plowed a gap in the disk, creating a barrier to the movement of dust, Yin said. Astronomers using the ALMA radio telescope in Chile have observed the same phenomenon in protoplanetary disks around other stars.

Crossing the Jupiter gap

Yet some meteorites seem to be exceptions to this general rule with a wider mixture of components.

Yin, UC Davis research scientist Curtis Williams, and their collaborators carried out a detailed study of isotopes from 30 meteorites. They confirmed that they fell into two distinct groups: the non-carbonaceous chondrites as well as other, more common types of meteorite; and the carbonaceous meteorites.

Then they studied individual chondrules from two chondritic meteorites, the Allende meteorite that fell in Mexico in 1969 and the Karoonda meteorite, which fell in Australia in 1930.

These meteorites turned out to contain chondrules from both the inner and outer solar system. Some material from the inner solar system must have managed to cross the Jupiter barrier to accrete with outer solar system chondrules into a meteorite that billions of years later would fall to Earth.

How? There are a couple of possible mechanisms, Williams said.

"One is that there was still movement along the disk midplane, although it should have been stopped by Jupiter," he said. "The other is that winds in the inner solar system could have lofted particles over the Jupiter gap."

Either of these mechanisms could also be responsible for inner solar system material that has also been found in comets by the Stardust mission.

The new study helps to connect cosmochemistry, planetary sciences and astronomy to give a complete picture of planet formation, Yin said.

An observer standing on Mars would see the planet's moon Phobos cross the sky from west to east every five hours. Its orbit passes between the sun and any given point on Mars about once each Earth year. Each time it does so, it causes from one to seven solar eclipses within the space of three days. One place where this happens is the site of NASA's InSight lander, stationed in the Elysium Planitia region since November 2018. In other words, the phenomenon occurs much more frequently than on Earth, when our moon crosses in front of the sun. "However, the eclipses on Mars are shorter - they last just 30 seconds and are never total eclipses," explains Simon Stähler, a seismologist at ETH Zurich's Institute of Geophysics. Photos taken by NASA's two Mars rovers, Opportunity and Curiosity, also show a sharp-?edged lump against the backdrop of the sun.

Photographs are not the only way to observe these transits. "When Earth experiences a solar eclipse, instruments can detect a decline in temperature and rapid gusts of wind, as the atmosphere cools in one particular place and air rushes away from that spot," Stähler explains. An analysis of the data from InSight should indicate whether similar effects are also detectable on Mars.

Waiting for 24 April 2020

In April 2019, the first series of solar eclipses were visible from InSight's landing site, but only some of the data it recorded was saved. Initial indications from that data prompted Stähler and an international research team to prepare excitedly for the next series of eclipses, due on 24 April 2020. They published the findings from their observations in August in the journal Geophysical Research Letters.

As expected, InSight's solar cells registered the transits. "When Phobos is in front of the sun, less sunlight reaches the solar cells, and these in turn produce less electricity," Stähler explains. "The decline in light exposure caused by Phobos's shadow can be measured." Indeed, the amount of sunlight dipped during an eclipse by 30 percent. However, InSight's weather instruments indicated no atmospheric changes, and the winds did not change as expected. Other instruments; however, delivered a surprise: both the seismometer and the magnetometer registered an effect.

Unusual signal from the seismometer

The signal from the magnetometer is most likely due to the decline in the solar cells' electricity, as Anna Mittelholz, a recent addition to ETH Zurich's Mars team, was able to show. "But we didn't expect this seismometer reading; it's an unusual signal," Stähler says. Normally, the instrument - equipped with electronics built at ETH - would indicate quakes on the planet. So far the Marsquake Service, led by John Clinton and Domenico Giardini at ETH, has recorded about 40 conventional quakes, the strongest of which registered a magnitude of 3.8, as well as several hundred regional, shallow quakes.

What was surprising during the solar eclipse was that the seismometer tilted slightly in a particular direction. "This tilt is incredibly small," Stähler notes. "Imagine a 5-?franc coin; now, push two silver atoms under one edge. That's the incline we're talking about: 10-8." As slight as this effect was, it was still unmistakable. "The most obvious explanation would be Phobos's gravity, similar to how Earth's moon causes the tides," Stähler says, "but we quickly ruled this out." If that were the explanation, then the seismometer signal would be present for a longer period of time and every five hours when Phobos makes its pass, not only during eclipses. Researchers determined the most likely cause of the tilt: "During an eclipse, the ground cools. It deforms unevenly, which tilts the instrument," says Martin van Driel from the Seismology and Wave Physics research group.

As it happens, an infrared sensor did indeed measure a cooling of the ground on Mars of two degrees. Calculations revealed that in the 30 seconds of the eclipse, the "cold front" could penetrate the ground only to a depth of micro-? or millimetres, but the effect was enough to tug at the seismometer.

Experiments in an old silver mine

An observation back on Earth supports Stähler's theory. At the Black Forest Observatory, located in an abandoned silver mine in Germany, Rudolf Widmer-?Schnidrig discovered a similar phenomenon: during a seismometer test, someone neglected to turn out the light. The heat given off by a 60-?watt bulb was apparently enough to warm the topmost layer of granite deep below ground, so that it expanded slightly and caused the seismometer to tilt slightly to one side.

Scientists should be able to use the tiny tilt signal from Mars to map Phobos' orbit with more precision than was previously possible. InSight's position is the most accurately measured location on Mars; if the scientists know exactly when a transit by Phobos here begins and ends, they can calculate its orbit precisely. This is important for future space missions. For example, Japan's space agency JAXA plans to send a probe to the moons of Mars in 2024 and bring samples from Phobos back to Earth. "To do that, they need to know exactly where they're flying to," says Stähler.

What precise orbit data reveals

Precise data on Phobos's orbit could also shed more light on the inner workings of Mars. While our moon continues to gain angular momentum and is steadily moving away from Earth, Phobos is slowing down and gradually falling back to Mars. In 30 to 50 million years, it will crash onto the planet's surface. "We can use this slight slowdown to estimate how elastic and thus how hot the Martian interior is; cold material is always more elastic than hot," explains Amir Khan, also at ETH Zurich's Institute of Geophysics. Ultimately, the researchers want to know if Mars was formed of the same material as Earth, or if different components could explain why Earth has plate tectonics, a dense atmosphere and conditions that support life - characteristics that Mars is lacking.

An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) found a peculiar dust ring system around the young triple star GW Orionis. The system has three large, misaligned rings with sufficient dust for planet formation. The misaligned rings might have been formed by a hidden planet between the rings, which would provide a clue to understand planet formation around a multiple star system.

The Sun is a single star, while many stars were formed in sets of two or more. Astronomers have found dozens of planetary systems around multiple-stars. However, no planets have ever been found around triple stars.

To examine the possibility of planets formed around triple stars, the international team of astronomers observed a young triple star system GW Orionis (Ori), 1300 light-years away from the Earth. GW Ori is composed of three stars; stars A and B with a separation of 1 astronomical unit (au), comparable with the distance between the Sun and the Earth, and the third star C with a separation of 8 au.

The ALMA observations revealed that GW Ori is surrounded by three rings made of small dust particles. The radii of the rings are 46, 188, and 336 au. Comparing to the fact that the size of the orbit of Neptune, the outermost planet in our Solar System, is 30 au, you can see how the rings of GW Ori are huge. There have been many rings imaged around young stars, but the outer ring of GW Ori is the largest ever.

The team estimated that the dust masses of the rings are 75, 170, and 245 Earth masses. "Each ring contains enough mass to form seeds of giant planets," says Takayuki Muto, a member of the research team and an astronomer at Kogakuin University in Japan.

The ALMA image of GW Ori shows another interesting feature. The innermost ring is greatly inclined against the outer two rings. "We were surprised to see the strong misalignment of the inner ring," says Jiaqing Bi of the University of Victoria in Canada, and leader of the team that published their results in The Astrophysical Journal Letters. "But the strange warp in the disk is confirmed by a twisted pattern that ALMA measured in the gas of the disk."

The team performed a computer simulation to investigate how the gravity of the central triple star affects the rings. "Our simulations show that the gravitational pull from the triple stars alone cannot explain the observed large misalignment. We think that the presence of a planet between these rings is needed to explain why the disk was torn apart," says a team member Nienke van der Marel of the University of Victoria. "This planet has likely carved a dust gap and broken the disk at the location of the current inner and outer rings," she adds.

"Astronomers have long discussed how planets are formed around multiple stars," explains Muto. "This observation paves the way to explore planet formation around a triple star system where gravitational effects are more complicated than around twin stars. I believe that research on the diversity of exoplanets will continue to make progress in the future."

Independently of Bi's team, a team of astronomers led by Stefan Kraus from the University of Exeter in the UK observed GW Ori with ALMA and the European Southern Observatory's Very Large Telescope (VLT). Near infrared observation with VLT showed for the first time that the innermost ring casts a shadow on the outer rings, which is clear evidence of disk misalignment. Kraus and his colleagues also performed a computer simulation and suggest that the triple star system can create misaligned rings, without gravitational assistance from planets. The two teams have different theories for the origin of the misaligned rings, but no conclusions have been reached so far. Nevertheless, GW Ori is a precious example to understand planet formation in the complex gravitational environment around multiple stars.

Pioneering new research has revealed the first direct evidence that groups of stars can tear apart their planet-forming disc, leaving it warped and with tilted rings.

An international team of experts, led by astronomers at the University of Exeter, has identified a stellar system where planet formation might take place in inclined dust and gas rings within a warped circumstellar disc around multiple stars.

A view from a potential planet around this system will give the observer a stunning view of a tilted, multiple stellar constellation - similar to Star Wars' Tatooine.

The results were made possible thanks to observations with the European Southern Observatory's Very Large Telescope (VLT), Georgia State University's Center for High-Angular Resolution Astronomy telescope array (CHARA), and the Atacama Large Millimeter/submillimeter Array (ALMA).

The research is the first output of a large programme on young stellar system that uses a pioneering infrared imager, called MIRC-X, that combines the light from all six telescopes of the CHARA telescope array. MIRC-X has been built by the Universities of Michigan and Exeter as part of a European Research Council-funded research project.

The instrument has been designed to give new insights into how star and planet formation is taking place within the rotating, circumstellar discs of dense dust and gas surrounding young stars.

Our Solar System is remarkably flat, with the planets all orbiting in the same plane. However, this is not always the case, especially for planet-forming discs around multiple stars, like the object of the new study: GW Orionis. This system, located just 1,200 light-years away in the constellation of Orion, has three stars and a deformed, broken-apart disc surrounding them.

Stefan Kraus, professor of astrophysics at the University of Exeter, who led the research published today in Science, said: "We're really excited that our new MIRC-X imager has provided the sharpest view yet of this intriguing system and revealed the gravitational dance of the three stars in the system. Normally, planets form around a flat disc of swirling dust and gas- yet our images reveal an extreme case where the disc is not flat at all.", said Stefan Kraus,

"Instead it is warped and has a misaligned ring that has broken away from the disc. The misaligned ring is located in the inner part of the disc, close to the three stars. The effect is that the view of a potential planet within this ring looks remarkably like that of Tatooine, of Star Wars fame."

The team observed the system with the SPHERE instrument on ESO's VLT and with ALMA, and were able to image the inner ring and confirm its misalignment. The team observed shadows that this ring casts on the rest of the disc. This helped them figure out the 3D shape of the rings and overall disc geometry.

The new research reveals that this inner ring contains 30 Earth masses of dust, which could be enough to form planets.

Alexander Kreplin of the University of Exeter, said: "Any planets formed within the misaligned ring will orbit the star on highly oblique orbits and we predict that many planets on oblique, wide-separation orbits will be discovered in future planet imaging surveys.

"Since more than half of stars in the sky are born with one or more companions, this raises an exciting prospect: there could be an unknown population of exoplanets that orbit their stars on very inclined and distant orbits."

To reach these conclusions, the team observed GW Orionis for over 11 years and mapped the orbit of the stars with unprecedented precision. Alison Young, a member of the team from the Universities of Exeter and Leicester, said: "We found that the three stars do not orbit in the same plane, but their orbits are misaligned with respect to each other and with respect to the disc."

The international team, with researchers from the UK, Belgium, Chile, France and the US, then combined their exhaustive observations with computer simulations to understand what had happened to the system. For the first time, they were able to clearly link the observed misalignments to the theoretical 'disc-tearing effect', which suggests that the conflicting gravitational pull of stars in different planes can warp and break their surrounding disc.

"We conducted simulations that show that the misalignment in the orbits of the three stars could cause the disc around them to break into distinct rings. This is what we see in the observations.", said Matthew Bate, professor of theoretical astrophysics at Exeter, who carried out some of the computer simulations on the system. "The observed shape of the inner ring also matches predictions on how the disc would tear."

Black holes can expel a thousand times more matter than they capture. The mechanism that governs both ejection and capture is the accretion disk, a vast mass of gas and dust spiraling around the black hole at extremely high speeds. The disk is hot and emits light as well as other forms of electromagnetic radiation. Part of the orbiting matter is pulled toward the center and disappears behind the event horizon, the threshold beyond which neither matter nor light can escape. Another, much larger, part is pushed further out by the pressure of the radiation emitted by the disk itself.

Every galaxy is thought to have a supermassive black hole at its center, but not all galaxies have, or still have, accretion disks. Those that do are known as active galaxies, on account of their active galactic nuclei. The traditional model posits two phases in the matter that accumulates in the central region of an active galaxy: a high-speed ionized gas outflow of matter ejected by the nucleus, and slower molecules that may flow into the nucleus.

A new model that integrates the two phases into a single scenario has now been put forward by Daniel May, a postdoctoral researcher in the University of São Paulo’s Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG-USP) in Brazil. “We found that the molecular phase, which appears to have completely different dynamics from the ionized phase, is also part of the outflow. This means there’s far more matter being blown away from the center, and the active galactic nucleus plays a much more important role in the structuring of the galaxy as a whole,” May told Agência FAPESP.

An article on the study by May and collaborators is published in the journal Monthly Notices of the Royal Astronomical Society. The study was supported by FAPESP via a doctoral scholarship and a postdoctoral scholarship awarded to May. João Steiner, Full Professor at IAG-USP and a co-author of the article, supervised May’s PhD and postdoc research.

May identified the pattern on the basis of a study of two active galaxies: NGC 1068, which he investigated in 2017, and NGC 4151, which he investigated in 2020. NGC stands for New General Catalogue of Nebulae and Clusters of Stars, established in the late nineteenth century.

“Using a highly meticulous image treatment methodology, we identified the same pattern in two very different galaxies. Most astronomers today are interested in studying very large datasets. Our approach was the opposite. We investigated the individual characteristics of these two objects in an almost artisanal manner,” May said.

“Our study suggests that initially a cloud of molecular gas in the central region of the galaxy collapses and activates its nucleus, forming the accretion disk. The photons emitted by the disk, which reaches temperatures on the order of a million degrees, push most of the gas a long way outward, while a smaller part of the gas is absorbed by the disk and eventually plunges into the black hole. As the cloud is sucked into the disk, two distinct phases take shape: one is ionized owing to exposure to the disk, and the other is molecular and overshadowed by its radiation. We discovered that the molecular part is entirely tied to the ionized part, which is known as the outflow. We were able to relate the two phases of the gas, previously considered disconnected, and fit their morphologies into a single scenario.”

The ionized gas derives from fragmentation of this molecular gas, May explained. As it fragments, it is pushed further out in an expanding hot bubble that can be as large as 300 light years in radius. For the sake of comparison, it is worth recalling that this is almost 70 times the distance from Earth to Proxima Centauri, the nearest star to the Solar System.

“When we observe the central regions of these two galaxies, we see this enormous bubble in profile, delineated by its walls of molecules,” May said. “We see the walls fragmenting and the ionized gas being driven out. The accretion disk appears as an extremely bright spot. All the information that reaches us from it corresponds to a pixel, so we don’t have enough resolution to discern its possible parts. The black hole is known about only from its effects.”

In the ancient Universe there was much more available gas, so the effect of a process such as that described by him was more intense, May explained. What he observed in relatively nearby galaxies such as NGC 1068 and NGC 4151 is a mild form of the process that occurred in more distant galaxies, whose active nuclei in the remote past are now detected as quasars.

The article “The nuclear architecture of NGC 4151: on the path toward a universal outflow mechanism in light of NGC 1068” can be retrieved from: academic.oup.com/mnras/article-abstract/496/2/1488/5851281?redirectedFrom=fulltext#205434907.

Journal

Monthly Notices of the Royal Astronomical Society

DOI

10.1093/mnras/staa1545

Strong interaction between plasmonic nanoparticles and free-space light induced the evanescently confined modes on the nanoparticle surfaces, which holds great promise in plasmonic nanophotonic technologies. Plasmonic nanoparticle with the capability of generating energetic charges makes it being widely exploited in the field of photocatalysis, providing a new paradigm for conversion renewable sunlight to useful fuels and high-value chemicals.

Plasmon metal nanoparticles/semiconductors with Schottky barrier at interface are well-received photocatalysts that can achieve charge spatial separation to prolong the lifetime of separating charge for matching the timescale of surface chemical reactions. The key question in the plasmonic photocatalysis is how plasmonic charges can be effectively separated to improve charge density at catalytic sites, which is critical to multi-hole/electron-driven redox reactions, such as water oxidation.

In natural photosynthesis, hundreds of functional pigments are distributed surrounding a reaction center of photosystem II to continuously supply photogenerated charges by increasing the light absorption flux. However, due to the lack of microscopic details of charge accumulation sites in artificial photosynthesis, there is less report for mimicking natural photosynthesis to extract sufficient hot holes in plasmonic photocatalysts for efficient oxygen evolution.

In a new research article published in the Beijing-based National Science Review, inspired by natural photosynthesis, Can Li and Fengtao Fan research group from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, present an elegant approach to simultaneously address the critical problems of light harvesting and charge density at catalytic sites of plasmonic photocatalyst. The group constructed Au nanoparticle dimers on TiO2 as optical antenna, and found charge accumulation at nanocavity of Au dimers/TiO2 photocatalyst mediated by surface plasmon resonance coupling. Combining experimentally measured surface photovoltage with theoretical calculations, the local density of hot hole was demonstrated to be related to the square of local near-field intensity. Using four-electron involved water oxidation reaction as a probe reaction, the performance of Au dimer/TiO2 photoanode can be improved by one order of magnitude compared to Au NPs/TiO2 photoanode.

The current work presents a previously unrecognized effect on charge accumulation at catalytic sites of plasmonic photocatalysts. Furthermore, it should encourage others to explore the significance of plasmonic hot spot to generate more charges - not only for photodetections, but also for photocatalysis associated with multiple charges transfer processes.

Every hour, the sun saturates the earth with more energy than humans use in a year. Harnessing some of this energy to meet global demand has become a grand challenge, with the world poised to double its energy consumption in just thirty years.

In a new study, researchers at the Biodesign Center for Applied Structural Discovery (CASD) and ASU's School of Molecular Sciences take a page from Nature's lesson book. Inspired by the way plants and other photosynthetic organisms collect and use the sun's radiant energy, they hope to develop technologies that harvest sunlight and store it as carbon-free or carbon-neutral fuels.

"This article describes a general yet useful strategy for better understanding the role of catalysts in emerging technologies for converting sunlight to fuels," says corresponding author Gary Moore.

The research appears in the current issue of the American Chemical Society (ACS) journal Applied Energy Materials and graces its cover.

Despite the advances in solar panel technologies, their limitations are apparent. Researchers would like to store accumulated energy from the sun in a concentrated form, to be used when and where it is needed. Catalysts--materials that act to speed up the rate at which chemical reactions occur--are a critical ingredient for harvesting sunlight and stockpiling it as fuels, through a process known as photoelectrosynthesis.

As the authors demonstrate, however, the effectiveness of catalysts is critically dependent on how they are used in new green technologies. The goal is to maximize energy efficiency and where possible, make use of earth-abundant elements.

According to Brian Wadsworth, researcher in the CASD center and lead author of the new study, a less-is-more approach to catalysts may improve the performance of photoelectrosynthetic devices:

"There is a traditional notion that relatively high loadings of catalyst are beneficial to maximizing the reaction rates and related performance of catalytic materials," Wadsworth says. "However, this design strategy should not always be implemented in assemblies involving the capture and conversion of solar energy as relatively thick catalyst layers can hamper performance by screening sunlight from reaching an underlying light-absorbing material and/or disfavoring the accumulation of catalytically-active states."

The new research provides a framework for better understanding catalytic performance in solar fuel devices and points the way to further discoveries.

WASHINGTON, Aug. 20, 2020 -- Many viruses, including HIV and influenza A, mutate so quickly that identifying effective vaccines or treatments is like trying to hit a moving target. A better understanding of viral propagation and evolution in single cells could help. Today, scientists report a new technique that can not only identify and quantify viral RNA in living cells, but also detect minor changes in RNA sequences that might give viruses an edge or make some people "superspreaders."

The researchers will present their results at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo. ACS is holding the meeting through Thursday. It features more than 6,000 presentations on a wide range of science topics.

A brand-new video about the research is available at http://www.acs.org/fall2020-outbreaks.

"For studying a new virus like SARS-CoV-2, it's important to understand not only how populations respond to the virus, but how individuals -- either people or cells -- interact with it," says Laura Fabris, Ph.D., the project's principal investigator. "So we've focused our efforts on studying viral replication in single cells, which in the past has been technically challenging."

Analyzing individual cells instead of large populations could go a long way toward better understanding many facets of viral outbreaks, such as superspreaders. That's a phenomenon in which some cells or people carry unusually high amounts of virus and therefore can infect many others. If researchers could identify single cells with high viral loads in superspreaders and then study the viral sequences in those cells, they could perhaps learn how viruses evolve to become more infectious or to outwit therapies and vaccines. In addition, features of the host cell itself could aid various viral processes and thus become targets for therapies. On the other end of the spectrum, some cells produce mutated viruses that are no longer infectious. Understanding how this happens could also lead to new antiviral therapies and vaccines.

But first, Fabris and colleagues at Rutgers University needed to develop an assay that was sensitive enough to detect viral RNA, and its mutations, in single living cells. The team based their technique on surface enhanced Raman spectroscopy (SERS), a sensitive method that detects interactions between molecules through changes in how they scatter light. The researchers decided to use the method to study influenza A. To detect the virus's RNA, they added to gold nanoparticles a "beacon DNA" specific to influenza A. In the presence of influenza A RNA, the beacon produced a strong SERS signal, whereas in the absence of this RNA, it did not. The beacon produced weaker SERS signals with increasing numbers of viral mutations, allowing the researchers to detect as few as two nucleotide changes. Importantly, the nanoparticles could enter human cells in a dish, and they produced a SERS signal only in those cells expressing influenza A RNA.

Now, Fabris and colleagues are making a version of the assay that produces a fluorescent signal, instead of a SERS signal, when viral RNA is detected. "SERS is not a clinically approved technology. It's just now breaking into the clinic," Fabris notes. "So we wanted to provide clinicians and virologists with an approach they would be more familiar with and have the technology to use right now." In collaboration with virologists and mathematicians at other universities, the team is developing microfluidic devices, or "lab-on-a-chip" technologies, to read many fluorescent samples simultaneously.

Because SERS is more sensitive, cheaper, faster and easier to perform than other assays based on fluorescence or the reverse transcriptase-polymerase chain reaction (known as RT-PCR), it could prove ideal for detecting and studying viruses in the future. Fabris is now collaborating with a company that makes a low-cost, portable Raman spectrometer, which would enable the SERS assay to be easily conducted in the field.

Fabris and her team are also working on identifying regions of the SARS-CoV-2 genome to target with SERS probes. "We're in the process of obtaining funding to work on possible SARS-CoV-2 diagnostics with the SERS method we developed," Fabris says.

The metabolic enzyme IL4I1 (Interleukin-4-Induced-1) promotes the spread of tumor cells and suppresses the immune system. This was discovered by scientists at the German Cancer Research Center (DKFZ) and the Berlin Institute of Health (BIH). The enzyme that activates the dioxin receptor is produced in large quantities by tumor cells. In the future, substances that inhibit IL4I1 could open up new opportunities for cancer therapy. The scientists have now published their results in the journal Cell.

Immunotherapies activate the body's own defense against tumors and are currently revolutionising cancer therapy. Despite some groundbreaking successes, however, only a small number of patients benefit from the drugs currently available. The teams led by Christiane Opitz and Martina Seiffert, both at the DKFZ, and Saskia Trump from BIH, investigated the molecular mechanisms by which tumors escape destruction by the immune system. Their research results may provide important information for the development of new immunotherapy concepts.

The aryl hydrocarbon receptor (AHR) is also known as dioxin receptor because it mediates the toxic effect of dioxins. However, not only toxins, but also the body's own metabolic products can activate the receptor. An example of this are degradation products of the amino acid tryptophane, which we take in with our food as a building block of proteins. Tumors use these metabolites to their advantage: They promote the mobility of cancer cells and weaken the immune response against tumors.

However, the metabolic pathways by which the relevant tryptophane degradation products are produced have not been sufficiently researched. To find out more, the scientists systematically investigated in 32 different types of cancer which tryptophane-degrading enzymes are associated with an activation of the dioxin receptor.

One molecule in particular caught the scientists' eye: the enzyme IL4I1. No other enzyme of the tryptophan metabolism was as strongly linked to an activation of the dioxin receptor as IL4I1: "The metabolites formed by IL4I1 bind to the dioxin receptor and activate it, which leads to the suppression of immune cells," explains Saskia Trump, BIH.

Of clinical interest is the observation that the survival probability of patients with gliomas, a type of malignant brain tumor, decreased when the enzyme was present in higher concentrations in these tumors.

In a mouse model for chronic lymphatic leukaemia (CLL), a type of blood cancer, IL4I1 was shown to promote cancer through its effects on the immune system. "In animals that do not produce IL4I1 in the tumor environment due to genetic alterations, the immune system is significantly more successful in preventing the cancer from progressing," explains Martina Seiffert of DKFZ.

"IL4I1 has great potential as a target for drugs. So far, drugs that inhibit enzymes of the tryptophan metabolism have failed in clinical trials because the tumors did not respond to them. However, the role of IL4I1 has so far been disregarded and this enzyme has not yet been tested as a target molecule," said Christiane Opitz.