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Shape matters for light-activated nanocatalysts

Points matter when designing nanoparticles that drive important chemical reactions using the power of light.

Researchers at Rice University’s Laboratory for Nanophotonics (LANP) have long known that a nanoparticle’s shape affects how it interacts with light, and their latest study shows how shape affects a particle’s ability to use light to catalyze important chemical reactions.

In a comparative study, LANP graduate students Lin Yuan and Minhan Lou and their colleagues studied aluminum nanoparticles with identical optical properties but different shapes. The most rounded had 14 sides and 24 blunt points. Another was cube-shaped, with six sides and eight 90-degree corners. The third, which the team dubbed “octopod,” also had six sides, but each of its eight corners ended in a pointed tip.

All three varieties have the ability to capture energy from light and release it periodically in the form of super-energetic hot electrons that can speed up catalytic reactions. Yuan, a chemist in the research group of LANP director Naomi Halas, conducted experiments to see how well each of the particles performed as photocatalysts for hydrogen dissociation reaction. The tests showed octopods had a 10 times higher reaction rate than the 14-sided nanocrystals and five times higher than the nanocubes. Octopods also had a lower apparent activation energy, about 45% lower than nanocubes and 49% lower than nanocrystals.

“The experiments demonstrated that sharper corners increased efficiencies,” said Yuan, co-lead author of the study, which is published in the American Chemical Society journal ACS Nano. “For the octopods, the angle of the corners is about 60 degrees, compared to 90 degrees for the cubes and more rounded points on the nanocrystals. So the smaller the angle, the greater the increase in reaction efficiencies. But how small the angle can be is limited by chemical synthesis. These are single crystals that prefer certain structures. You cannot make infinitely more sharpness.”

Lou, a physicist and study co-lead author in the research group of LANP’s Peter Nordlander, verified the results of the catalytic experiments by developing a theoretical model of the hot electron energy transfer process between the light-activated aluminum nanoparticles and hydrogen molecules.

“We input the wavelength of light and particle shape,” Lou said. “Using these two aspects, we can accurately predict which shape will produce the best catalyst.”

The work is part of an ongoing green chemistry effort by LANP to develop commercially viable light-activated nanocatalysts that can insert energy into chemical reactions with surgical precision. LANP has previously demonstrated catalysts for ethylene and syngas production, the splitting of ammonia to produce hydrogen fuel and for breaking apart “forever chemicals.”

“This study shows that photocatalyst shape is another design element engineers can use to create photocatalysts with the higher reaction rates and lower activation barriers,” said Halas, Rice’s Stanley C. Moore Professor of Electrical and Computer Engineering, director of Rice’s Smalley-Curl Institute and a professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering.

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Quirky response to magnetism presents quantum physics mystery

The search is on to discover new states of matter, and possibly new ways of encoding, manipulating, and transporting information. One goal is to harness materials’ quantum properties for communications that go beyond what’s possible with conventional electronics. Topological insulators — materials that act mostly as insulators but carry electric current across their surface — provide some tantalizing possibilities.

“Exploring the complexity of topological materials — along with other intriguing emergent phenomena such as magnetism and superconductivity — is one of the most exciting and challenging areas of focus for the materials science community at the U.S. Department of Energy’s Brookhaven National Laboratory,” said Peter Johnson, a senior physicist in the Condensed Matter Physics & Materials Science Division at Brookhaven. “We’re trying to understand these topological insulators because they have lots of potential applications, particularly in quantum information science, an important new area for the division.”

For example, materials with this split insulator/conductor personality exhibit a separation in the energy signatures of their surface electrons with opposite “spin.” This quantum property could potentially be harnessed in “spintronic” devices for encoding and transporting information. Going one step further, coupling these electrons with magnetism can lead to novel and exciting phenomena.

“When you have magnetism near the surface you can have these other exotic states of matter that arise from the coupling of the topological insulator with the magnetism,” said Dan Nevola, a postdoctoral fellow working with Johnson. “If we can find topological insulators with their own intrinsic magnetism, we should be able to efficiently transport electrons of a particular spin in a particular direction.”

In a new study just published and highlighted as an Editor’s Suggestion in Physical Review Letters, Nevola, Johnson, and their coauthors describe the quirky behavior of one such magnetic topological insulator. The paper includes experimental evidence that intrinsic magnetism in the bulk of manganese bismuth telluride (MnBi2Te4) also extends to the electrons on its electrically conductive surface. Previous studies had been inconclusive as to whether or not the surface magnetism existed.

But when the physicists measured the surface electrons’ sensitivity to magnetism, only one of two observed electronic states behaved as expected. Another surface state, which was expected to have a larger response, acted as if the magnetism wasn’t there.

“Is the magnetism different at the surface? Or is there something exotic that we just don’t understand?” Nevola said.

Johnson leans toward the exotic physics explanation: “Dan did this very careful experiment, which enabled him to look at the activity in the surface region and identify two different electronic states on that surface, one that might exist on any metallic surface and one that reflected the topological properties of the material,” he said. “The former was sensitive to the magnetism, which proves that the magnetism does indeed exist in the surface. However, the other one that we expected to be more sensitive had no sensitivity at all. So, there must be some exotic physics going on!”

The measurements

The scientists studied the material using various types of photoemission spectroscopy, where light from an ultraviolet laser pulse knocks electrons loose from the surface of the material and into a detector for measurement.

“For one of our experiments, we use an additional infrared laser pulse to give the sample a little kick to move some of the electrons around prior to doing the measurement,” Nevola explained. “It takes some of the electrons and kicks them [up in energy] to become conducting electrons. Then, in very, very short timescales — picoseconds — you do the measurement to look at how the electronic states have changed in response.”

The map of the energy levels of the excited electrons shows two distinct surface bands that each display separate branches, electrons in each branch having opposite spin. Both bands, each representing one of the two electronic states, were expected to respond to the presence of magnetism.

To test whether these surface electrons were indeed sensitive to magnetism, the scientists cooled the sample to 25 Kelvin, allowing its intrinsic magnetism to emerge. However only in the non-topological electronic state did they observe a “gap” opening up in the anticipated part of the spectrum.

“Within such gaps, electrons are prohibited from existing, and thus their disappearance from that part of the spectrum represents the signature of the gap,” Nevola said.

The observation of a gap appearing in the regular surface state was definitive evidence of magnetic sensitivity — and evidence that the magnetism intrinsic in the bulk of this particular material extends to its surface electrons.

However, the “topological” electronic state the scientists studied showed no such sensitivity to magnetism — no gap.

“That throws in a bit of a question mark,” Johnson said.

“These are properties we’d like to be able to understand and engineer, much like we engineer the properties of semiconductors for a variety of technologies,” Johnson continued.

In spintronics, for example, the idea is to use different spin states to encode information in the way positive and negative electric charges are presently used in semiconductor devices to encode the “bits” — 1s and 0s — of computer code. But spin-coded quantum bits, or qubits, have many more possible states — not just two. This will greatly expand on the potential to encode information in new and powerful ways.

“Everything about magnetic topological insulators looks like they’re right for this kind of technological application, but this particular material doesn’t quite obey the rules,” Johnson said.

So now, as the team continues their search for new states of matter and further insights into the quantum world, there’s a new urgency to explain this particular material’s quirky quantum behavior.

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Zooming in on dark matter

Cosmologists have zoomed in on the smallest clumps of dark matter in a virtual universe — which could help us to find the real thing in space.

An international team of researchers, including Durham University, UK, used supercomputers in Europe and China to focus on a typical region of a computer-generated universe.

The zoom they were able to achieve is the equivalent of being able to see a flea on the surface of the Moon.

This allowed them to make detailed pictures and analyses of hundreds of virtual dark matter clumps (or haloes) from the very largest to the tiniest.

Dark matter particles can collide with dark matter anti-particles near the centre of haloes where, according to some theories, they are converted into a burst of energetic gamma-ray radiation.

Their findings, published in the journal Nature, could mean that these very small haloes could be identified in future observations by the radiation they are thought to give out.

Co-author Professor Carlos Frenk, Ogden Professor of Fundamental Physics at the Institute for Computational Cosmology, at Durham University, UK, said: “By zooming in on these relatively tiny dark matter haloes we can calculate the amount of radiation expected to come from different sized haloes.

“Most of this radiation would be emitted by dark matter haloes too small to contain stars and future gamma-ray observatories might be able to detect these emissions, making these small objects individually or collectively ‘visible’.

“This would confirm the hypothesised nature of the dark matter, which may not be entirely dark after all.”

Most of the matter in the universe is dark (apart from the gamma radiation they emit in exceptional circumstances) and completely different in nature from the matter that makes up stars, planets and people.

The universe is made of approximately 27 per cent dark matter with the rest largely consisting of the equally mysterious dark energy. Normal matter, such as planets and stars, makes up a relatively small five per cent of the universe.

Galaxies formed and grew when gas cooled and condensed at the centre of enormous clumps of this dark matter — so-called dark matter haloes.

Astronomers can infer the structure of large dark matter haloes from the properties of the galaxies and gas within them.

The biggest haloes contain huge collections of hundreds of bright galaxies, called galaxy clusters, weighing a 1,000 trillion times more than our Sun.

However, scientists have no direct information about smaller dark matter haloes that are too tiny to contain a galaxy. These can only be studied by simulating the evolution of the Universe in a large supercomputer.

The smallest are thought to have the same mass as the Earth according to current popular scientific theories about dark matter that underlie the new research.

The simulations were carried out using the Cosmology Machine supercomputer, part of the DiRAC High-Performance Computing facility in Durham, funded by the Science and Technology Facilities Council (STFC), and computers at the Chinese Academy of Sciences.

By zooming-in on the virtual universe in such microscopic detail, the researchers were able to study the structure of dark matter haloes ranging in mass from that of the Earth to a big galaxy cluster.

Surprisingly, they found that haloes of all sizes have a very similar internal structure and are extremely dense at the centre, becoming increasingly spread out, with smaller clumps orbiting in their outer regions.

The researchers said that without a measure scale it was almost impossible to tell an image of a dark matter halo of a massive galaxy from one of a halo with a mass a fraction of the Sun’s.

Co-author Professor Simon White, of the Max Planck Institute of Astrophysics, Germany, said: “We expect that small dark matter haloes would be extremely numerous, containing a substantial fraction of all the dark matter in the universe, but they would remain mostly dark throughout cosmic history because stars and galaxies grow only in haloes more than a million times as massive as the Sun.

“Our research sheds light on these small haloes as we seek to learn more about what dark matter is and the role it plays in the evolution of the universe.”

The research team, led by the National Astronomical Observatories of the Chinese Academy of Sciences, and including Durham University, UK, the Max Planck Institute for Astrophysics, Germany, and the Center for Astrophysics in Harvard, USA, took five years to develop, test and carry out their cosmic zoom.

The research was funded by the STFC, the European Research Council, the Chinese Academy of Sciences, the Max Planck Society and Harvard University.

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New evidence for quantum fluctuations near a quantum critical point in a superconductor

Among all the curious states of matter that can coexist in a quantum material, jostling for preeminence as temperature, electron density and other factors change, some scientists think a particularly weird juxtaposition exists at a single intersection of factors, called the quantum critical point or QCP.

“Quantum critical points are a very hot issue and interesting for many problems,” says Wei-Sheng Lee, a staff scientist at the Department of Energy’s SLAC National Accelerator Laboratory and investigator with the Stanford Institute for Materials and Energy Sciences (SIMES). “Some suggest that they’re even analogous to black holes in the sense that they are singularities — point-like intersections between different states of matter in a quantum material — where you can get all sorts of very strange electron behavior as you approach them.”

Lee and his collaborators reported in Nature Physics today that they have found strong evidence that QCPs and their associated fluctuations exist. They used a technique called resonant inelastic X-ray scattering (RIXS) to probe the electronic behavior of a copper oxide material, or cuprate, that conducts electricity with perfect efficiency at relatively high temperatures.

These so-called high-temperature superconductors are a bustling field of research because they could give rise to zero-waste transmission of energy, energy-efficient transportation systems and other futuristic technologies, although no one knows the underlying microscopic mechanism behind high-temperature superconductivity yet. Whether QCPs exist in cuprates is also a hotly debated issue.

In experiments at the UK’s Diamond Light Source, the team chilled the cuprate to temperatures below 90 kelvins (minus 183 degrees Celsius), where it became superconducting. They focused their attention on what’s known as charge order — alternating stripes in the material where electrons and their negative charges are denser or more sparse.

The scientists excited the cuprate with X-rays and measured the X-ray light that scattered into the RIXS detector. This allowed them to map out how the excitations propagated through the material in the form of subtle vibrations, or phonons, in the material’s atomic lattice, which are hard to measure and require very high-resolution tools.

At the same time, the X-rays and the phonons can excite electrons in the charge order stripes, causing the stripes to fluctuate. Since the data obtained by RIXS reflects the coupling between the behavior of the charge stripes and the behavior of the phonons, observing the phonons allowed the researchers to measure the behavior of the charge order stripes, too.

What the scientists expected to see is that when the charge order stripes grew weaker, their excitations would also fade away. “But what we observed was very strange,” Lee said. “We saw that when charge order became weaker in the superconducting state, the charge order excitations became stronger. This is a paradox because they should go hand in hand, and that’s what people find in other charge order systems.”

He added, “To my knowledge this is the first experiment about charge order that has shown this behavior. Some have suggested that this is what happens when a system is near a quantum critical point, where quantum fluctuations become so strong that they melt the charge order, much like heating ice increases thermal vibrations in its rigid atomic lattice and melts it into water. The difference is that quantum melting, in principle, occurs at zero temperature.” In this case, Lee said, the unexpectedly strong charge order excitations seen with RIXS were manifestations of those quantum fluctuations.

Lee said the team is now studying these phenomena at a wider range of temperatures and at different levels of doping — where compounds are added to change the density of freely moving electrons in the material — to see if they can nail down exactly where the quantum critical point could be in this material.

Thomas Devereaux, a theorist at SIMES and senior author of the report, noted that many phases of matter can be intertwined in cuprates and other quantum materials.

“Superconducting and magnetic states, charge order stripes and so on are so entangled that you can be in all of them at the same time,” he said. “But we’re stuck in our classical way of thinking that they have to be either one way or another.”

Here, he said, “We have an effect, and Wei-Sheng is trying to measure it in detail, trying to see what’s going on.”

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When Dirac meets frustrated magnetism

The fields of condensed matter physics and material science are intimately linked because new physics is often discovered in materials with special arrangements of atoms. Crystals, which have repeating units of atoms in space, can have special patterns which result in exotic physical properties. Particularly exciting are materials which host multiple types of exotic properties because they give scientists the opportunity to study how those properties interact with and influence each other. The combinations can give rise to unexpected phenomena and fuel years of basic and technological research.

In a new study published in Science Advances this week, an international team of scientists from the USA, Columbia, Czech Republic, England, and led by Dr. Mazhar N. Ali at the Max Planck Institute of Microstructure Physics in Germany, has shown that a new material, KV3Sb5, has a never-seen-before combination of properties that results in one of the largest anomalous Hall effects (AHEs) ever observed; 15,500 siemens per centimeter at 2 Kelvin.

Discovered in the lab of co-author Prof. Tyrel McQueen at Johns Hopkins University, KV3Sb5 combines four properties into one material: Dirac physics, metallic frustrated magnetism, 2D exfoliability (like graphene), and chemical stability.

Dirac physics, in this context, relates to the fact that the electrons in KV3Sb5 aren’t just your normal run-of-the-mill electrons; they are moving extremely fast with very low effective mass. This means that they are acting “light-like”; their velocities are becoming comparable to the speed of light and they are behaving as though they have only a small fraction of the mass which they should have. This results in the material being highly metallic and was first shown in graphene about 15 years ago.

The “frustrated magnetism” arises when the magnetic moments in a material (imagine little bar magnets which try to turn each other and line up North to South when you bring them together) are arranged in special geometries, like triangular nets. This scenario can make it hard for the bar magnets to line up in way that they all cancel each other out and are stable. Materials exhibiting this property are rare, especially metallic ones. Most frustrated magnet materials are electrical insulators, meaning that their electrons are immobile. “Metallic frustrated magnets have been highly sought after for several decades. They have been predicted to house unconventional superconductivity, Majorana fermions, be useful for quantum computing, and more,” commented Dr. Ali.

Structurally, KV3Sb5 has a 2D, layered structure where triangular vanadium and antimony layers loosely stack on top of potassium layers. This allowed the authors to simply use tape to peel off a few layers (a.k.a. flakes) at a time. “This was very important because it allowed us to use electron-beam lithography (like photo-lithography which is used to make computer chips, but using electrons rather than photons) to make tiny devices out of the flakes and measure properties which people can’t easily measure in bulk.” remarked lead author Shuo-Ying Yang, from the Max Planck Institute of Microstructure Physics. “We were excited to find that the flakes were quite stable to the fabrication process, which makes it relatively easy to work with and explore lots of properties.”

Armed with this combination of properties, the team first chose to look for an anomalous Hall effect (AHE) in the material. This phenomenon is where electrons in a material with an applied electric field (but no magnetic field) can get deflected by 90 degrees by various mechanisms. “It had been theorized that metals with triangular spin arrangements could host a significant extrinsic effect, so it was a good place to start,” noted Yang. Using angle resolved photoelectron spectroscopy, microdevice fabrication, and a low temperature electronic property measurement system, Shuo-Ying and co-lead author Yaojia Wang (Max Planck Institute of Microstructure Physics) were able to observe one of the largest AHE’s ever seen.

The AHE can be broken into two general categories: intrinsic and extrinsic. “The intrinsic mechanism is like if a football player made a pass to their teammate by bending the ball, or electron, around some defenders (without it colliding with them),” explained Ali. “Extrinsic is like the ball bouncing off of a defender, or magnetic scattering center, and going to the side after the collision. Many extrinsically dominated materials have a random arrangement of defenders on the field, or magnetic scattering centers randomly diluted throughout the crystal. KV3Sb5 is special in that it has groups of 3 magnetic scattering centers arranged in a triangular net. In this scenario, the ball scatters off of the cluster of defenders, rather than a single one, and is more likely to go to the side than if just one was in the way.” This is essentially the theorized spin-cluster skew scattering AHE mechanism which was demonstrated by the authors in this material. “However the condition with which the incoming ball hits the cluster seems to matter; you or I kicking the ball isn’t the same as if, say, Christiano Ronaldo kicked the ball,” added Ali. “When Ronaldo kicks it, it is moving way faster and bounces off of the cluster with way more velocity, moving to the side faster than if just any average person had kicked it. This is, loosely speaking, the difference between the Dirac quasiparticles (Ronaldo) in this material vs normal electrons (average person) and is related to why we see such a large AHE,” Ali laughingly explained.

These results may also help scientists identify other materials with this combination of ingredients. “Importantly, the same physics governing this AHE could also drive a very large spin Hall effect (SHE) — where instead of generating an orthogonal charge current, an orthogonal spin current is generated,” remarked Wang. “This is important for next-generation computing technologies based on an electron’s spin rather than its charge.”

“This is a new playground material for us: metallic Dirac physics, frustrated magnetism, exfoliatable, and chemically stable all in one. There is a lot of opportunity to explore fun, weird phenomena, like unconventional superconductivity and more,” said Ali, excitedly.

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Challenging a central dogma of chemistry: Energy flow in chemical reactions

Steve Granick, Director of the IBS Center for Soft and Living Matter and Dr. Huan Wang, Senior Research Fellow, report together with 5 interdisciplinary colleagues in the July 31 issue of the journal Science that common chemical reactions accelerate Brownian diffusion by sending long-range ripples into the surrounding solvent.

The findings violate a central dogma of chemistry, that molecular diffusion and chemical reaction are unrelated. To observe that molecules are energized by chemical reaction is “new and unknown,” said Granick. “When one substance transforms to another by breaking and forming bonds, this actually makes the molecules move more rapidly. It’s as if the chemical reactions stir themselves naturally.”

“Currently, Nature does an excellent job of producing molecular machines but in the natural world scientists have not understood well enough how to design this property,” said Wang. “Beyond curiosity to understand the world, we hope that practically this can become useful in guiding thinking about transducing chemical energy for molecular motion in liquids, for nanorobotics, precision medicine and greener material synthesis.”

The unexpected ripples generated by chemical reactions, especially when catalyzed (accelerated by substances not themselves consumed), propagate long-range. For chemists and physicists, this work challenges the textbook view that molecular motion and chemical reaction are decoupled, and that reactions affect only the nearby vicinity. For engineers, this work shows a powerful new approach to design nanomotors at the truly molecular level.

Screening 15 organic chemical reactions, the researchers study chemical reactions that are workhorses with wide application within the organic chemical, pharmaceutical and materials industries. For example, “click” reactions assist the assembly of libraries of biomedical compounds for screening and the “Grubbs” reaction used for plastic manufacture. Their economic impact is major. Estimates indicate that a majority of all products manufactured require catalysis somewhere in their production sequence.

Wang remarked with enthusiasm: “Now, we’re like a baby taking her first steps and there’s so much exciting opportunity to grow this baby.”

In designing their study, the researchers were bio-inspired by noticing that motion can be powered by enzymes and other molecular motors that are prevalent in living systems. Pioneering earlier work by Dr. Ah-Young Jee in the same research center showed this. But there was no consensus among scientists if these reports could be correctly extended outside biology. Analyzing the problem, the researchers made a high-risk, high-payoff argument. They hypothesized that the phenomenon would form an approach to understand molecular machines in the real world.

Testing their hypothesis, the team developed new analytical techniques. Professor Tsvi Tlusty, a theorist, predicted that catalysts in reaction gradients should migrate “uphill” in the direction of lesser diffusivity. Professor Yoon-Kyoung Cho, a microfluidics expert, designed a tailor-made microfluidics chip to test this idea. Dr. Ruoyu Dong, a Research Fellow, performed numerical computer simulations. “Our interdisciplinary team responded incredibly quickly to the research opportunities thanks to the research freedom of the Korean Institute for Basic Science,” said Granick.

The team presents guidelines showing that the magnitude of diffusion increase in different systems depends on the energy release rate. These guidelines can be useful practically to estimate the effect in as-yet untested reactions. Beyond this, the study is very useful for expanding understanding of active materials, a collective term that traditionally refers to things like cells and microorganisms.

Granick concluded: “The field of active materials, quite new and growing fast, is enriched by this discovery that chemical reactions behave as nanoswimmers made of individual molecules that stir up the reaction soup. The concept of active materials has shown its value in challenging a central dogma of chemistry.”

These findings were published in the July 31, 2020 issue of Science magazine. The study was performed at the IBS Center for Soft and Living Matter by authors Huan Wang, Myeonggon Park, Ruoyu Dong, Junyoung Kim, Yoon-Kyoung Cho, Tsvi Tlusty, and Steve Granick.

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Should You Hire A Developer Or Use The API For Your Website’s CMS?

It doesn’t matter how powerful or well-rounded your chosen CMS happens to be: there can still come a point at which you decide that its natural state isn’t enough and something more is needed. It could be a new function, a fresh perspective, or improved performance, and you’re unwilling to settle for less. What should you do?

Your instinct might be to hire a web developer, ideally one with some expertise in that particular CMS, but is that the right way to go? Developers can be very costly, and whether you have some coding skill or you’re a total novice, you might be able to get somewhere without one — and the key could be using the API for your CMS.

In this post, we’re going to consider why you might want to hire a developer, why you should investigate APIs, and how you can choose between these options. Let’s get to it.

Why you should hire a developer

It’s fairly simple to make a case for hiring a web developer. For one thing, it’s easy. By sharing the load, you get to preserve your existing workload and collaborate with an expert, a second pair of eyes that can complete your vision and deftly deal with any issues that might arise. Additionally, it’s the best way to get quick results if you’re willing to allocate enough money to afford a top-notch developer and make your project a priority.

The ease of this option explains why it’s so popular. We so often outsource things that would be easy to do ourselves (getting store-bought sandwiches, using cleaning services, etc.) that outsourcing something as complex as a website development project seems like an obvious choice for anyone who isn’t themselves a programmer with plenty of free time.

And even if you are a programmer with enough free time to take on a personal project, you might not have the right skills for the job. Every system has its own nuances, whether it’s a powerful platform with proprietary parts (like Shopify) or an open-source foundation built around ease of use (like Ghost), so getting a CMS expert can make for a smoother experience.

Why you should use the API for your CMS

So, with such a good argument to be made for immediately consulting a developer, why should you take the time to get involved directly? Well, one of the core goals of an API — as you may well be aware — is to make system functions readily accessible to outside systems, and you can take advantage of that to extend your system through integrations.

Becoming familiar with the workings of an API doesn’t require you to have an exhaustive knowledge of the CMS itself. You need only understand the available fields and functions and how you can call them (and interact with them) from elsewhere. From there, it’s more about finding — or creating — the external systems that can give you the results you need.

The best developer portals will have detailed API references along with getting started guides, sample code, SDKs and everything else a developer needs to successfully consume the API. The providers  behind them want as many people as possible to gravitate towards their platforms, after all more compatible modules (along with services like Zapier) means a stronger ecosystem and more interest overall. This means that even people with relatively meager technical understanding can get somewhere.

Additionally, getting to know the API for your CMS will help you understand what the system can and can’t do natively. It’s possible that by consuming the API you will uncover existing functionality that you otherwise wouldn’t have noticed. Overall, then, taking this step first will help you understand your CMS and either source an existing integration or build a more economical outline of a project that you can then pass to a developer.

How you can choose the right approach

In talking about building a project outline, I hinted at the natural conclusion here, which is that these options aren’t mutually exclusive. Having studied the API for your website’s CMS, you can develop something else or bring in a suitable module, but you can also continue to work with an external developer. It doesn’t subtract from your options. For that reason, then, I strongly recommend working with the API first and seeing what you can glean from it. That will allow you to make the smartest decision about how to proceed.

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Manipulating tiny skyrmions with small electric currents

A research group from the RIKEN Center for Emergent Matter Science have managed to manipulate and track the movement of individual magnetic vortices called skyrmions, which have been touted as strong candidates to act as information carriers in next-generation storage devices and as synapses for neuromorphic computing, They were able to move and measure skyrmions of 80 nanometers in size, using a small electric current a thousand times weaker than those used for drives of magnetic domain walls in the racetrack memory.

This work could be key to the creation of a new type of device called “skyrmion-based racetrack” memory, , which uses topological electron-spin textures, allowing much greater energy efficiency that conventional electronic devices. Essentially, this type of memory involves using currents of spin-aligned electricity to put a magnetic domain past magnetic “read/write heads” — information carriers which act as either ones or zeroes. In the case of skyrmions, the existence and non-existence of a skyrmion can serve as a bit of information. What has proven difficult, however, is in effectively measuring skyrmions without using high currents of electricity.

In the current work, published in Science Advances, the group, led by Xiuzhen Yu of the RIKEN Center for Emergent Matter Science, set out working with a thin film of iron germanide, a type of material known as a helimagnet, making it easier to manipulate the small magnetic vortices called skyrmions. Importantly, the film used for the study was developed with a notch, which allowed the spin current to be localized in a specific area near the corner of the notch.

Normally, skyrmions emerge as part of a structure called a skyrmion crystal, which incorporates a number of vortices and hence is quite difficult to move. An important goal of research has been to isolate and manipulate individual skyrmions, making it easier to move them, but this is a tricky process. By experimenting with the directional currents, and recording the results with sequential Lorentz transmission electron microscopy, the group found a point where they could isolate individual skyrmions, and record how they moved based on known processes such as the topological Hall effect.

According to Xiuzhen Yu, who led the research group, “Through this work we have demonstrated that it is possible to manipulate and track individual skyrmions and its crystal using a relatively low electric current, and we hope that this will help the development of more energy efficient racetrack memory as well as neuromorphic computing. We realize that there are limitations in terms of how much the skyrmions can be moved, and plan to work, by developing a bilayer system that can host combined skyrmions, to further improve the device to enable it to be put into practical application.”

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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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ScienceDaily

A new type of matter discovered inside neutron stars

A Finnish research group has found strong evidence for the presence of exotic quark matter inside the cores of the largest neutron stars in existence. The conclusion was reached by combining recent results from theoretical particle and nuclear physics to measurements of gravitational waves from neutron star collisions.

All normal matter surrounding us is composed of atoms, whose dense nuclei, comprising protons and neutrons, are surrounded by negatively charged electrons. Inside what are called neutron stars, atomic matter is, however, known to collapse into immensely dense nuclear matter, in which the neutrons and protons are packed together so tightly that the entire star can be considered one single enormous nucleus.

Up until now, it has remained unclear whether inside the cores of the most massive neutron stars nuclear matter collapses into an even more exotic state called quark matter, in which the nuclei themselves no longer exist. Researchers from the University of Helsinki now claim that the answer to this question is yes. The new results were published in the journal Nature Physics.

“Confirming the existence of quark cores inside neutron stars has been one of the most important goals of neutron star physics ever since this possibility was first entertained roughly 40 years ago,” says Associate Professor Aleksi Vuorinen from the University of Helsinki’s Department of Physics.

Existence very likely

With even large-scale simulations run on supercomputers unable to determine the fate of nuclear matter inside neutron stars, the Finnish research group proposed a new approach to the problem. They realised that by combining recent findings from theoretical particle and nuclear physics with astrophysical measurements, it might be possible to deduce the characteristics and identity of matter residing inside neutron stars.

In addition to Vuorinen, the group includes doctoral student Eemeli Annala from Helsinki, as well as their colleagues Tyler Gorda from the University of Virginia, Aleksi Kurkela from CERN, and Joonas Nättilä from Columbia University.

According to the study, matter residing inside the cores of the most massive stable neutron stars bears a much closer resemblance to quark matter than to ordinary nuclear matter. The calculations indicate that in these stars the diameter of the core identified as quark matter can exceed half of that of the entire neutron star. However, Vuorinen points out that there are still many uncertainties associated with the exact structure of neutron stars. What does it mean to claim that quark matter has almost certainly been discovered?

“There is still a small but nonzero chance that all neutron stars are composed of nuclear matter alone. What we have been able to do, however, is quantify what this scenario would require. In short, the behaviour of dense nuclear matter would then need to be truly peculiar. For instance, the speed of sound would need to reach almost that of light,” Vuorinen explains.

Radius determination from gravitational wave observations

A key factor contributing to the new findings was the emergence of two recent results in observational astrophysics: the measurement of gravitational waves from a neutron star merger and the detection of very massive neutron stars, with masses close to two solar masses.

In the autumn of 2017, the LIGO and Virgo observatories detected, for the first time, gravitational waves generated by two merging neutron stars. This observation set a rigorous upper limit for a quantity called tidal deformability, which measures the susceptibility of an orbiting star’s structure to the gravitational field of its companion. This result was subsequently used to derive an upper limit for the radii of the colliding neutron stars, which turned out to be roughly 13 km.

Similarly, while the first observation of a neutron star dates back all the way to 1967, accurate mass measurements of these stars have only been possible for the past 20 years or so. Most stars with accurately known masses fall inside a window of between 1 and 1.7 stellar masses, but the past decade has witnessed the detection of three stars either reaching or possibly even slightly exceeding the two-solar-mass limit.

Further observations expected

Somewhat counterintuitively, information about neutron star radii and masses has already considerably reduced the uncertainties associated with the thermodynamic properties of neutron star matter. This has also enabled completing the analysis presented by the Finnish research group in their Nature Physics article.

In the new analysis, the astrophysical observations were combined with state-of-the-art theoretical results from particle and nuclear physics. This enabled deriving an accurate prediction for what is known as the equation of state of neutron star matter, which refers to the relation between its pressure and energy density. An integral component in this process was a well-known result from general relativity, which relates the equation of state to a relation between the possible values of neutron star radii and masses.

Since the autumn of 2017, a number of new neutron star mergers have been observed, and LIGO and Virgo have quickly become an integral part of neutron star research. It is precisely this rapid accumulation of new observational information that plays a key role in improving the accuracy of the new findings of the Finnish research group, and in confirming the existence of quark matter inside neutron stars. With further observations expected in the near future, the uncertainties associated with the new results will also automatically decrease.

“There is reason to believe that the golden age of gravitational wave astrophysics is just beginning, and that we will shortly witness many more leaps like this in our understanding of nature,” Vuorinen rejoices.

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