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How to have a blast like a black hole

Laser Engineering at Osaka University have successfully used short, but extremely powerful laser blasts to generate magnetic field reconnection inside a plasma. This work may lead to a more complete theory of X-ray emission from astronomical objects like black holes.

In addition to being subjected to extreme gravitational forces, matter being devoured by a black hole can be also be pummeled by intense heat and magnetic fields. Plasmas, a fourth state of matter hotter than solids, liquids, or gasses, are made of electrically charged protons and electrons that have too much energy to form neutral atoms. Instead, they bounce frantically in response to magnetic fields. Within a plasma, magnetic reconnection is a process in which twisted magnetic field lines suddenly “snap” and cancel each other, resulting in the rapid conversion of magnetic energy into particle kinetic energy. In stars, including our sun, reconnection is responsible for much of the coronal activity, such as solar flares. Owing to the strong acceleration, the charged particles in the black hole’s accretion disk emit their own light, usually in the X-ray region of the spectrum.

To better understand the process that gives rise to the observed X-rays coming from black holes, scientists at Osaka University used intense laser pulses to create similarly extreme conditions on the lab. “We were able to study the high-energy acceleration of electrons and protons as the result of relativistic magnetic reconnection,” Senior author Shinsuke Fujioka says. “For example, the origin of emission from the famous black hole Cygnus X-1, can be better understood.”

This level of light intensity is not easily obtained, however. For a brief instant, the laser required two petawatts of power, equivalent to one thousand times the electric consumption of the entire globe. With the LFEX laser, the team was able to achieve peak magnetic fields with a mind-boggling 2,000 telsas. For comparison, the magnetic fields generated by an MRI machine to produce diagnostic images are typically around 3 teslas, and Earth’s magnetic field is a paltry 0.00005 teslas. The particles of the plasma become accelerated to such an extreme degree that relativistic effects needed to be considered.

“Previously, relativistic magnetic reconnection could only be studied via numerical simulation on a supercomputer. Now, it is an experimental reality in a laboratory with powerful lasers,” first author King Fai Farley Law says. The researchers believe that this project will help elucidate the astrophysical processes that can happen at places in the Universe that contain extreme magnetic fields.

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A tiny instrument to measure the faintest magnetic fields

Physicists at the University of Basel have developed a minuscule instrument able to detect extremely faint magnetic fields. At the heart of the superconducting quantum interference device are two atomically thin layers of graphene, which the researchers combined with boron nitride. Instruments like this one have applications in areas such as medicine, besides being used to research new materials.

To measure very small magnetic fields, researchers often use superconducting quantum interference devices, or SQUIDs. In medicine, their uses include monitoring brain or heart activity, for example, while in the earth sciences researchers use SQUIDs to characterize the composition of rocks or detect groundwater flows. The devices also have a broad range of uses in other applied fields and basic research.

The team led by Professor Christian Schönenberger of the University of Basel’s Department of Physics and the Swiss Nanoscience Institute has now succeeded in creating one of the smallest SQUIDs ever built. The researchers described their achievement in the scientific journal Nano Letters.

A superconducting ring with weak links

A typical SQUID consists of a superconducting ring interrupted at two points by an extremely thin film with normal conducting or insulating properties. These points, known as weak links, must be so thin that the electron pairs responsible for superconductivity are able to tunnel through them. Researchers recently also began using nanomaterials such as nanotubes, nanowires or graphene to fashion the weak links connecting the two superconductors.

As a result of their configuration, SQUIDs have a critical current threshold above which the resistance-free superconductor becomes a conductor with ordinary resistance. This critical threshold is determined by the magnetic flux passing through the ring. By measuring this critical current precisely, the researchers can draw conclusions about the strength of the magnetic field.

SQUIDs with six layers

“Our novel SQUID consists of a complex, six-layer stack of individual two-dimensional materials,” explains lead author David Indolese. Inside it are two graphene monolayers separated by a very thin layer of insulating boron nitride. “If two superconducting contacts are connected to this sandwich, it behaves like a SQUID — meaning it can be used to detect extremely weak magnetic fields.”

In this setup, the graphene layers are the weak links, although in contrast to a regular SQUID they are not positioned next to each other, but one on top of the other, aligned horizontally. “As a result, our SQUID has a very small surface area, limited only by the constraints of nanofabrication technology,” explains Dr. Paritosh Karnatak from Schönenberger’s team.

The tiny device for measuring magnetic fields is only around 10 nanometers high — roughly a thousandth of the thickness of a human hair. The instrument can trigger supercurrents that flow in minuscule spaces. Moreover, its sensitivity can be adjusted by changing the distance between the graphene layers. With the help of electrical fields, the researchers are also able to increase the signal strength, further enhancing the measurement accuracy.

Analyzing topological insulators

The Basel research team’s primary goal in developing the novel SQUIDs was to analyze the edge currents of topological insulators. Topological insulators are currently a focus of countless research groups all over the world. On the inside, they behave like insulators, while on the outside — or along the edges — they conduct current almost losslessly, making them possible candidates for a broad range of applications in the field of electronics.

“With the new SQUID, we can determine whether these lossless supercurrents are due to a material’s topological properties, and thereby tell them apart from non-topological materials. This is very important for the study of topological insulators,” remarked Schönenberger of the project. In future, SQUIDs could also be used as low-noise amplifiers for high-frequency electrical signals, or for instance to detect local brainwaves (magnetoencephalography), as their compact design means a large number of the devices can be connected in series.

The paper is the outcome of close collaboration among groups at the University of Basel, the University of Budapest and the National Institute for Material Science in Tsukuba (Japan).

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ProgrammableWeb

UnifyID Launches Gait-Based Biometric Authentication API

Standard methods for biometric authentication, think fingerprint scanning and facial recognition, are extremely problematic given the current cultural expectation that masks, and often gloves, be worn throughout the day. UnifyID has launched a new gait-based biometric authentication API that hopes to solve these problems. 

The new UnifyID GaitAuth API provides developers with a more passive version of biometric authentication. By analyzing the way that a user walks, a collection of attributes that are highly individualized, the API is able to authenticate a user in the background, without direct interaction on the users part. This allows for the device that the resulting application is running on to become a hardware key of sorts.

UnifyID makes all this happen by leaning on proprietary machine-learning algorithms that do all the work in the background. The company points to this as an advantage. One of the challenges of properly implementing biometric authentication is having users submit enough high-quality data for the engine to authenticate with a high level of certainty. By collecting this data in the background via a passive process, gait analysis is able to ensure sufficient data. 

Developers can check out UnifyID’s documentation for the API and SDK.

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Author: <a href="https://www.programmableweb.com/user/%5Buid%5D">KevinSundstrom</a>

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Quantum physics: Physicists develop a new theory for Bose-Einstein condensates

Bose-Einstein condensates are often described as the fifth state of matter: At extremely low temperatures, gas atoms behave like a single particle. The exact properties of these systems are notoriously difficult to study. In the journal Physical Review Letters, physicists from Martin Luther University Halle-Wittenberg (MLU) and Ludwig Maximilian University Munich have proposed a new theory to describe these quantum systems more effectively and comprehensively.

Research into the exotic state of matter dates back to Albert Einstein, who predicted the theoretical existence of Bose-Einstein condensates in 1924. “Many attempts were made to prove their existence experimentally,” says Dr Carlos Benavides-Riveros from the Institute of Physics at MLU. Finally, in 1995, researchers in the U.S. succeeded in producing the condensates in experiments. In 2001 they received the Nobel Prize for Physics for their work. Since then, physicists around the world have been working on ways to better define and describe these systems that would enable their behaviour to be more accurately predicted.

This normally requires extremely complex equations and models. “In quantum mechanics, the Schrödinger equation is used to describe systems with many interacting particles. But because the number of degrees of freedom increases exponentially, this equation is not easy to solve. This is the so-called many-body problem and finding a solution to this problem is one of the major challenges of theoretical and computational physics today,” explains Benavides-Riveros. The working group at MLU is now proposing a method that is comparatively simple. “One of our key insights is that the particles in the condensate interact only in pairs,” says co-author Jakob Wolff from MLU. This enables these systems to be described using much simpler and more established methods, like those used in electronic quantum systems.

“Our theory is in principle exact and can be applied to different physical regimes and scenarios, for example strongly interacting ultracold atoms. And it looks like it will be also a promising way to describe superconducting materials,” concludes Jakob Wolff.

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What if mysterious ‘cotton candy’ planets actually sport rings?

Some of the extremely low-density, “cotton candy like” exoplanets called super-puffs may actually have rings, according to new research published in The Astronomical Journal by Carnegie’s Anthony Piro and Caltech’s Shreyas Vissapragada

Super-puffs are notable for having exceptionally large radii for their masses — which would give them seemingly incredibly low densities. The adorably named bodies have been confounding scientists since they were first discovered, because they are unlike any planets in our Solar System and challenge our ideas of what distant planets can be like.

“We started thinking, what if these planets aren’t airy like cotton candy at all,” Piro said. “What if the super-puffs seem so large because they are actually surrounded by rings?”

In our own Solar System, all of the gas and ice giant planets have rings, with the most well-known example being the majestic rings of Saturn. But it has been difficult for astronomers to discover ringed planets orbiting distant stars.

The radii of exoplanets are measured during transits — when the exoplanet crosses in front of its host star causing a dip in the star’s light. The greater the size of the dip, the larger the exoplanet.

“We started to wonder, if you were to look back at us from a distant world, would you recognize Saturn as a ringed planet, or would it appear to be a puffy planet to an alien astronomer?” Vissapragada asked.

To test this hypothesis, Piro and Vissapragada simulated how a ringed exoplanet would look to an astronomer with high-precision instruments watching it transit in front of its host star. They also investigated the types of ring material that could account for observations of super-puffs.

Their work demonstrated that rings could explain some, but not all, of the super-puffs that NASA’s Kepler mission has discovered so far.

“These planets tend to orbit in close proximity to their host stars, meaning that the rings would have to be rocky, rather than icy,” Piro explained. “But rocky ring radii can only be so big, unless the rock is very porous, so not every super-puff would fit these constraints.”

According to Piro and Vissapragada, three super-puffs are especially good candidates for rings — Kepler 87c and 177c as well as HIP 41378f.

Follow-up observations to confirm their work won’t be possible until NASA’s James Webb Space Telescope launches next year, because existing land- and space-based telescopes lack the precision to confirm the presence of rings around these distant worlds.

If some of the super-puffs could be confirmed as ringed, this would improve astronomers’ understanding of how these planetary systems formed and evolved around their host stars.

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Galactic gamma-ray sources reveal birthplaces of high-energy particles

Nine sources of extremely high-energy gamma rays comprise a new catalog compiled by researchers with the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory. All produce gamma rays with energies over 56 trillion electron volts (TeV) and three emit gamma rays extending to 100 TeV and beyond, making these the highest-energy sources ever observed in our galaxy. The catalog helps to explain where the particles originate and how they are accelerated to such extremes.

“The Earth is constantly being bombarded with charged particles called cosmic rays, but because they are charged, they bend in magnetic fields and don’t point back to their sources. We rely on gamma rays, which are produced close to the sources of the cosmic rays, to narrow down their origins,” said Kelly Malone, an astrophysicist in the Neutron Science and Technology group at Los Alamos National Laboratory and a member of the HAWC scientific collaboration. “There are still many unanswered questions about cosmic-ray origins and acceleration. High energy gamma rays are produced near cosmic-ray sites and can be used to probe cosmic-ray acceleration. However, there is some ambiguity in using gamma rays to study this, as high-energy gamma rays can also be produced via other mechanisms, such as lower-energy photons scattering off of electrons, which commonly occurs near pulsars.”

The newly cataloged astrophysical gamma-ray sources have energies about 10 times higher than can be produced using experimental particle colliders on Earth. While higher-energy astrophysical particles have been previously detected, this is the first time specific galactic sources have been pinpointed. All of the sources have extremely energetic pulsars (highly magnetized rotating neutron stars) nearby. The number of sources detected may indicate that ultra-high-energy emission is a generic feature of powerful particle winds coming from pulsars embedded in interstellar gas clouds known as nebulae, and that more detections will be forthcoming.

The HAWC Gamma-Ray Observatory consists of an array of water-filled tanks sitting high on the slopes of the Sierra Negra volcano in Puebla, Mexico, where the atmosphere is thin and offers better conditions for observing gamma rays. When these gamma rays strike molecules in the atmosphere they produce showers of energetic particles. Although nothing can travel faster than the speed of light in a vacuum, light moves more slowly through water. As a result, some particles in cosmic ray showers travel faster than light in the water inside the HAWC detector tanks. The faster-than-light particles, in turn, produce characteristic flashes of light called Cherenkov radiation. By recording the Cherenkov flashes in the HAWC water tanks, researchers can reconstruct the sources of the particle showers to learn about the particles that caused them in the first place.

The HAWC collaborators plan to continue searching for the sources of high-energy cosmic rays. By combining their data with measurements from other types of observatories such as neutrino, x-ray, radio and optical telescopes, they hope to disentangle the astrophysical mechanisms that produce the cosmic rays that continuously rain down on our planet.

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Untangling links between nitrogen oxides and airborne sulfates helps tackle hazy air pollution

Dense, hazy fog episodes characterized by relatively high humidity, low visibility and extremely high PM2.5 have been a headache to many megacities including those in Mainland China. Among pollutants that are less than 2.5 microns in diameter (PM2.5), airborne sulfate is one of the most common components of hazy air pollution formed atmospherically via the oxidation of sulphur dioxide (SO2).

While the reactant-product link between sulphur dioxide and airborne sulfate formation is common knowledge, the complex oxidants and mechanisms that enable this transformation are not. In particular, the role of nitrogen oxides in sulfate production is unclear. Managing sulfate pollution has dogged researchers and governments alike as it is not produced directly from pollution sources, unlike nitrogen oxides which are clearly emitted from vehicle exhaust, and the combustion of fossil fuels like coal, diesel and natural gas. This is the first study systematically examining the multiple roles of nitrogen oxides in affecting oxidants that enable this set of chemical reactions.

In collaboration with the California Institute of Technology, a research team led by Prof. YU Jianzhen, Professor at HKUST’s Department of Chemistry and Division of Environment and Sustainability, identified three formation mechanism regimes, corresponding to the three distinct roles that nitrogen oxides play in sulfate production depending on the chemical surroundings. Under low NOx conditions, NOx catalyze the cycling of hydroxyl radicals, an effective oxidant of SO2, and thus promote formation of sulfate. Under extremely high NOx common in haze-fog conditions, NOx act as dominant oxidants of SO2 and thus also promote formation of sulfate. But in an environment with medium-high level of NOx, nitrogen dioxide (a member of the NOx family) would actually serve as a sink for hydroxyl radicals which supresses the oxidation of sulphur dioxide and thus inhibits sulfate formation.

These findings indicate that in order to reduce sulfate levels in highly polluted haze-fog conditions, co-control of SO2 and NOx emissions is necessary. However, since NOx would inhibit sulfate formation when its emissions are intermediately high, suppressing NOx in such environment would thus bring up sulfate levels in the air.

“Since sulfate is formed atmospherically and cannot be controlled directly, we must target its precursor components (such as sulphur dioxide and nitrogen oxides). Effective reduction of sulfate content in the air relies on knowledge of the quantitative relationship it has with its precursors. This work lays the conceptual framework to delineate the relationship between sulfate and one set of its controllable precursors, nitrogen oxides (NOx) — the low and extremely high concentration of NOx could both fuel up the production of sulfate. The policymakers should pay attention to when they try to control the emission of NOx,” explained Prof. Yu.

As sulfate is one of the major components which leads to haze formation and acid rain, this study laid the groundwork for formulating more effective measures of targeting this major pollutant involved in aforementioned events — which do not just block the views or make aquatic environments more acidic, but also compromise human health. With greater understanding and better control, this will lead to improved air quality and better protection of public health and ecological systems as a whole.

The team’s findings were recently published in the scientific journal Nature Geoscience.

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Visible light and nanoparticle catalysts produce desirable bioactive molecules

Northwestern University chemists have used visible light and extremely tiny nanoparticles to quickly and simply make molecules that are of the same class as many lead compounds for drug development.

Driven by light, the nanoparticle catalysts perform chemical reactions with very specific chemical products — molecules that don’t just have the right chemical formulas but also have specific arrangements of their atoms in space. And the catalyst can be reused for additional chemical reactions.

The semiconductor nanoparticles are known as quantum dots — so small that they are only a few nanometers across. But the small size is power, providing the material with attractive optical and electronic properties not possible at greater length scales.

“Quantum dots behave more like organic molecules than metal nanoparticles,” said Emily A. Weiss, who led the research. “The electrons are squeezed into such a small space that their reactivity follows the rules of quantum mechanics. We can take advantage of this, along with the templating power of the nanoparticle surface.”

This work, published recently by the journal Nature Chemistry, is the first use of a nanoparticle’s surface as a template for a light-driven reaction called a cycloaddition, a simple mechanism for making very complicated, potentially bioactive compounds.

“We use our nanoparticle catalysts to access this desirable class of molecules, called tetrasubstituted cyclobutanes, through simple, one-step reactions that not only produce the molecules in high yield, but with the arrangement of atoms most relevant for drug development,” Weiss said. “These molecules are difficult to make any other way.”

Weiss is the Mark and Nancy Ratner Professor of Chemistry in the Weinberg College of Arts and Sciences. She specializes in controlling light-driven electronic processes in quantum dots and using them to perform light-driven chemistry with unprecedented selectivity.

The nanoparticle catalysts use energy from visible light to activate molecules on their surfaces and fuse them together to form larger molecules in configurations useful for biological applications. The larger molecule then detaches easily from the nanoparticle, freeing the nanoparticle to be used again in another reaction cycle.

In their study, Weiss and her team used three-nanometer nanoparticles made of the semiconductor cadmium selenide and a variety of starter molecules called alkenes in solution. Alkenes have core carbon-carbon double bonds which are needed to form the cyclobutanes.

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Creating 2D heterostructures for future electronics

Nanomaterials could provide the basis of many emerging technologies, including extremely tiny, flexible, and transparent electronics.

While many nanomaterials exhibit promising electronic properties, scientists and engineers are still working to best integrate these materials together to eventually create semiconductors and circuits with them.

Northwestern Engineering researchers have created two-dimensional (2D) heterostructures from two of these materials, graphene and borophene, taking an important step toward creating intergrated circuits from these nanomaterials.

“If you were to crack open an integrated circuit inside a smartphone, you’d see many different materials integrated together,” said Mark Hersam, Walter P. Murphy Professor of Materials Science and Engineering, who led the research. “However, we’ve reached the limits of many of those traditional materials. By integrating nanomaterials like borophene and graphene together, we are opening up new possibilities in nanoelectronics.”

Supported by the Office for Naval Research and the National Science Foundation, the results were published October 11 in the journal Science Advances. In addition to Hersam, applied physics PhD student Xiaolong Liu co-authored this work.

Creating a new kind of heterostructure

Any integrated circuit contains many materials that perform different functions, like conducting electricity or keeping components electrically isolated. But while transistors within circuits have become smaller and smaller — thanks to advances in materials and manufacturing — they are close to reaching the limit of how small they can get.

Ultrathin 2D materials like graphene have the potential to bypass that problem, but integrating 2D materials together is difficult. These materials are only one atom thick, so if the two materials’ atoms do not line up perfectly, the integration is unlikely to be successful. Unfortunately, most 2D materials do not match up at the atomic scale, presenting challenges for 2D integrated circuits.

Borophene, the 2D version of boron that Hersam and coworkers first synthesized in 2015, is polymorphic, meaning it can take on many different structures and adapt itself to its environment. That makes it an ideal candidate to combine with other 2D materials, like graphene.

To test whether it was possible to integrate the two materials into a single heterostructure, Hersam’s lab grew both graphene and borophene on the same substrate. They grew the graphene first, since it grows at a higher temperature, then deposited boron on the same substrate and let it grow in regions where there was no graphene. This process resulted in lateral interfaces where, because of borophene’s accommodating nature, the two materials stitched together at the atomic scale.

Measuring electronic transitions

The lab characterized the 2D heterostructure using a scanning tunneling microscope and found that the electronic transition across the interface was exceptionally abrupt — which means it could be ideal for creating tiny electronic devices.

“These results suggest that we can create ultrahigh density devices down the road,” Hersam said. Ultimately, Hersam hopes to achieve increasingly complex 2D structures that lead to novel electronic devices and circuits. He and his team are working on creating additional heterostructures with borophene, combining it with an increasing number of the hundreds of known 2D materials.

“In the last 20 years, new materials have enabled miniaturization and correspondingly improved performance in transistor technology,” he said. “Two-dimensional materials have the potential to make the next leap.”

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Hackster.io

You Can Now Purchase a Breakout Shield for Your TinyPICO ESP32 Board

The Espressif ESP32 module, like its predecessor the ESP8266, has become extremely popular among makers. It’s a very inexpensive microcontroller with a respectable processor and amount of memory, and comes equipped with built-in WiFi and Bluetooth connectivity. There are a lot of development boards on the market to take advantage of the ESP32 module, but TinyPICO is one of the smallest and most feature-packed. Now you can purchase a breakout shield for your TinyPICO boards.

The entire purpose of the TinyPICO ESP32 board is to be as small as possible, while still integrating features, such as LiPo battery management, to avoid the need for additional components. Both the size and capabilities are uncommon among other ESP32 development boards. That small size does, however, make it somewhat difficult to prototype your projects.

That’s why TinyPICO’s creator, Brain Lough, has developed a breakout shield that makes all of the pins easily accessible through screw terminals. Now you can wire up your TinyPICO projects without doing any soldering, before moving onto a more permanent solution once you’ve tested your prototype. Best of all, the TinyPICO breakout shield costs just $14.00 on Tindie!

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Author: Cameron Coward