A colorful detector: Crystalline material reversibly changes color when absorbing water

Researchers at the University of Tsukuba have developed a new kind of color-shifting crystalline material that can be used to indicate the presence of water. The change in hue is dramatic enough to be gauged by the unaided human eye. This work could lead to the creation of highly sensitive “vapochromic” sensors that can show if a particular gas or water vapor is present without the need for external power.

Chemical sensors are important to many industrial processes. To ensure safety and efficiency, factories often need to be monitored for potentially toxic gasses or even excess humidity. Sensors for water vapor are particularly important, but may have limited lifetimes or require external power. To address this, scientists at the University of Tsukuba have invented a new crystalline material that changes color when exposed to water vapor. Inside the crystal, long branching molecules called dendrimers are held together by van der Waals forces.

“The aromatic carbazole dendrimers containing carbon rings are anchored to a dibenzophenazine core,” explains senior author Professor Yohei Yamamoto. “Interestingly, even though van der Waals forces are usually considered to be relatively weak, the crystal stays together during operation.”

The research team also extensively characterized the new material. In addition to studying the color in both the hydrated and dehydrated states using spectroscopy, the scientists used techniques including single-crystal and powder X-ray diffraction analysis, as well as thermogravimetric analysis. On the basis of the experimental results and theoretical density functional theory calculations, they were able to determine the molecular mechanism responsible for the different appearances under different water concentrations. The color-shifting properties of the crystal come from conformation changes in the dendrimers. Upon exposure to water vapor, the planes of the outermost carbazole units in the crystal twist simultaneously. This motion changes the energies of the electronic orbitals, which causes the electrons to absorb different colors of light.

“We believe that our findings will lead to the further exploration of van der Waals porous crystals, much like metal-organic frameworks that have found a place in chemistry,” Professor Yamamoto says. “This work can lead to a new class of gas sensors that can work in difficult to reach locations, because they do not require external power.”

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Quantum body scanner? What happens when vector vortex beams meet scattering media

Propagate light through any kind of medium — be it free space or biological tissue — and light will scatter. Robustness to scattering is a common requirement for communications and for imaging systems. Structured light, with its use of projected patterns, is resistant to scattering, and has therefore emerged as a versatile tool. In particular, modes of structured light carrying orbital angular momentum (OAM) have attracted significant attention for applications in biomedical imaging.

OAM is an internal property of light conferring a characteristic doughnut shape to the spatial profile. The polarization profile of OAM modes of light can also be structured. Superimpose two OAM modes, and you can get a vector vortex beam (VVB) characterized by a doughnut intensity distribution in the beam cross-section, and with spatially variant polarization. VVBs are considered suitable and advantageous for quantum applications in medical technology.

An innovative cancer scanner

An international team of researchers recently published a comprehensive study of VVB transmission in scattering media. The team is collaborating under the aegis of the European Union’s FET-OPEN project Cancer Scan, which proposes to develop a radically new unified technological concept of biomedical detection deploying new ideas in quantum optics and quantum mechanics. The new concept is based on unified transmission and detection of photons in a three-dimensional space of orbital angular momentum, entanglement, and hyperspectral characteristics. Theoretically, these elements can contribute to developing a scanner that can screen for cancer and detect it in a single scan of the body, without any risk of radiation.

As explained in their report, the team implemented a flexible platform to generate VVBs and Gaussian beams, and investigated their propagation through a medium that mimics the features of biological tissue. They demonstrate and analyze the degradation of both the spatial profile and polarization pattern of the different modes of light.

Ready, aim, scatter

For both Gaussian beams and VVBs, the authors remark that spatial profiles undergo an abrupt change as the concentration of the medium increases beyond 0.09%: a sudden swift decrease in contrast. The authors observe that the change is due to the presence of a uniform background caused by the scattered components of the beams.

Investigating the polarization profiles, they found that VVB behavior is quite different from that of the Gaussian beams. Gaussian beams present a uniform polarization pattern that is unaffected by the scattering process. In contrast, VVBs present a complex distribution of polarization on the transverse plane. The team observed that a portion of the VVB signal becomes completely depolarized when it passes through scattering media, but a portion of the signal preserves its structure.

These insights into how interaction with scattering media can affect the behavior of structured OAM light represent a step forward in exploring how it may interact with biological tissue. The team hopes that their comprehensive study will stimulate further investigation into the effects of light-scattering tissue-mimicking media, to advance the quest for innovative biomedical detection technology.

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Materials provided by SPIE–International Society for Optics and Photonics. Note: Content may be edited for style and length.

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A binary star as a cosmic particle accelerator

Scientists have identified the binary star Eta Carinae as a new kind of source for very high-energy (VHE) cosmic gamma-radiation. Eta Carinae is located 7500 lightyears away in the constellation Carina in the Southern Sky and, based on the data collected, emits gamma rays with energies up to 400 gigaelectronvolts (GeV), some 100 billion times more than the energy of visible light.

With a specialised telescope in Namibia a DESY-led team of researchers has proven a certain type of binary star as a new kind of source for very high-energy cosmic gamma-radiation. Eta Carinae is located 7500 lightyears away in the constellation Carina (the ship’s keel) in the Southern Sky and, based on the data collected, emits gamma rays with energies all the way up to 400 gigaelectronvolts (GeV), some 100 billion times more than the energy of visible light. The team headed by DESY’s Stefan Ohm, Eva Leser and Matthias Füßling is presenting its findings, made at the gamma-ray observatory High Energy Stereoscopic System (H.E.S.S.), in the journal Astronomy & Astrophysics. An accompanying multimedia animation explains the phenomenon. “With such visualisations we want to make the fascination of research tangible,” emphasises DESY’s Director of Astroparticle Physics, Christian Stegmann.

Eta Carinae is a binary system of superlatives, consisting of two blue giants, one about 100 times, the other about 30 times the mass of our sun. The two stars orbit each other every 5.5 years in very eccentric elliptical orbits, their separation varying approximately between the distance from our Sun to Mars and from the Sun to Uranus. Both these gigantic stars fling dense, supersonic stellar winds of charged particles out into space. In the process, the larger of the two loses a mass equivalent to our entire Sun in just 5000 years or so. The smaller one produces a fast stellar wind travelling at speeds around eleven million kilometres per hour (about one percent of the speed of light).

A huge shock front is formed in the region where these two stellar winds collide, heating up the material in the wind to extremely high temperatures. At around 50 million degrees Celsius, this matter radiates brightly in the X-ray range. The particles in the stellar wind are not hot enough to emit gamma radiation, though. “However, shock regions like this are typically sites where subatomic particles are accelerated by strong prevailing electromagnetic fields,” explains Ohm, who is the head of the H.E.S.S. group at DESY. When particles are accelerated this rapidly, they can also emit gamma radiation. In fact, the satellites “Fermi,” operated by the US space agency NASA, and AGILE, belonging to the Italian space agency ASI, already detected energetic gamma rays of up to about 10 GeV coming from Eta Carinae in 2009.

“Different models have been proposed to explain how this gamma radiation is produced,” Füßling reports. “It could be generated by accelerated electrons or by high-energy atomic nuclei.” Determining which of these two scenarios is correct is crucial: very energetic atomic nuclei account for the bulk of the so-called Cosmic Rays, a subatomic cosmic hailstorm striking Earth constantly from all directions. Despite intense research for more than 100 years, the sources of the Cosmic Rays are still not exhaustively known. Since the electrically charged atomic nuclei are deflected by cosmic magnetic fields as they travel through the universe, the direction from which they arrive at Earth no longer points back to their origin. Cosmic gamma rays, on the other hand, are not deflected. So, if the gamma rays emitted by a specific source can be shown to originate from high-energy atomic nuclei, one of the long-sought accelerators of cosmic particle radiation will have been identified.

“In the case of Eta Carinae, electrons have a particularly hard time getting accelerated to high energyies, because they are constantly being deflected by magnetic fields during their acceleration, which makes them lose energy again,” says Leser. “Very high-energy gamma radiation begins above the 100 GeV range, which is rather difficult to explain in Eta Carinae to stem from electron acceleration.” The satellite data already indicated that Eta Carinae also emits gamma radiation beyond 100 GeV, and H.E.S.S. has now succeeded in detecting such radiation up to energies of 400 GeV around the time of the close encounter of the two blue giants in 2014 and 2015. This makes the binary star the first known example of a source in which very high-energy gamma radiation is generated by colliding stellar winds.

“The analysis of the gamma radiation measurements taken by H.E.S.S. and the satellites shows that the radiation can best be interpreted as the product of rapidly accelerated atomic nuclei,” says DESY’s PhD student Ruslan Konno, who has published a companion study, together with scientists from the Max Planck Institute for Nuclear Physics in Heidelberg. “This would make the shock regions of colliding stellar winds a new type of natural particle accelerator for cosmic rays.” With H.E.S.S., which is named after the discoverer of Cosmic Rays, Victor Franz Hess, and the upcoming Cherenkov Telescope Array (CTA), the next-generation gamma-ray observatory currently being built in the Chilean highlands, the scientists hope to investigate this phenomenon in greater detail and discover more sources of this kind.

“I find science and scientific research extremely important,” says Nicolai, who sees close parallels in the creative work of artists and scientists. For him, the appeal of this work also lay in the artistic mediation of scientific research results: “particularly the fact that it is not a film soundtrack, but has a genuine reference to reality,” emphasizes the musician and artist. Together with the exclusively composed sound, this unique collaboration of scientists, animation artists and musician has resulted in a multimedia work that takes viewers on an extraordinary journey to a superlative double star some 7500 light years away.

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Laser technology: The Turbulence and the Comb

It is a very special kind of light, which can be used for important measurements: so-called frequency combs play a major role in laser research today. While the light of an ordinary laser only has one single, well-defined wavelength, a frequency comb consists of different light frequencies, which are precisely arranged at regular distances, much like the teeth of a comb.

Such frequency combs are difficult to generate. However, an international research team from Austria (TU Wien, Vienna), the USA (Harvard, Yale) and Italy (Milan, Turin) has now succeeded in producing this special kind of light, using simple circular quantum cascade lasers — a result that seemed to contradict conventional laser theories completely. As it turned out, turbulences, as they are known from aerodynamics or water waves, are responsible for this particularly ordered type of light. These results have now been published in the scientific journal Nature.

Better than Physics Permits?

“Actually, we were first looking for something very different in our experiments,” says Benedikt Schwarz, who researches frequency combs at TU Wien (Vienna) and Harvard University, and was awarded an ERC Starting Grant for his research in 2019. “We were investigating circular quantum cascade lasers, which is a special type of laser that has been manufactured in our laboratories at the Institute of Solid State Electronics for years. We wanted to investigate how certain defects affect the laser light.” But much to the scientists’ surprise, they found out that these circular mini-lasers can be used in a very simple way to produce frequency combs, which are composed of several light frequencies, arranged at equal distances.

“This is great for us, because this is exactly the kind of light we are looking for. Only we didn’t expect to find it in this particular experiment — the success seemed to contradict current laser theory,” explains Schwarz.

If the light from a laser is to consist of different frequencies at the same time, then the light cannot be constant — it must vary in time. An oscillation is required, repeating itself in a regular pattern. Only then, a frequency comb is created.

Turbulence can Cause Chaos — or Order

“When we thought about how this oscillation could be explained, we looked for similar phenomena in other scientific fields. Eventually we came across turbulence as the driving force that causes the oscillation leading to our frequency combs,” says Benedikt Schwarz. Turbulence is a phenomenon that arises in many very different areas: In the smoke that emerges from an extinguished candle, turbulence can be seen that leads to chaotic, unpredictable patterns. But so-called wave instabilities can be found in all types of waves. A small disturbance gets bigger and bigger and eventually dominates the dynamics of the system.

The mathematical connection between such turbulence effects and the novel laser light could finally be found by a laser theory that Nikola Opa?ak from the Vienna University of Technology had recently published in November 2019: “We found that this laser theory can be connected to the same mathematical equation that also describes turbulence in other scientific disciplines,” says Schwarz.

In a ring-shaped laser, wave instabilities can cause a stable frequency comb to form. In addition, there is a strong connection between different light frequencies — different frequencies are firmly coupled to each other.

The Comb as an Artificial Nose

Frequency combs play an important role in research mainly because they can be used to build tiny chemical sensors. Many molecules absorb light in the infrared range in a very characteristic way. By measuring which wavelengths are being absorbed, it is possible to determine which molecules are present. To do this, however, it is necessary to have as many different light frequencies in the infrared range available as possible — and this is exactly what an optical frequency comb provides in an ideal way.

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‘One-way’ electronic devices enter the mainstream

Waves, whether they are light waves, sound waves, or any other kind, travel in the same manner in forward and reverse directions — this is known as the principle of reciprocity. If we could route waves in one direction only — breaking reciprocity — we could transform a number of applications important in our daily lives. Breaking reciprocity would allow us to build novel “one-way” components such as circulators and isolators that enable two-way communication, which could double the data capacity of today’s wireless networks. These components are essential to quantum computers, where one wants to read a qubit without disturbing it. They are also critical to radar systems, whether in self-driving cars or those used by the military.

A team led by Harish Krishnaswamy, professor of electrical engineering, is the first to build a high-performance non-reciprocal device on a compact chip with a performance 25 times better than previous work. Power handling is one of the most important metrics for these circulators and Krishnaswamy’s new chip can handle several watts of power, enough for cellphone transmitters that put out a watt or so of power. The new chip was the leading performer in a DARPA SPAR (Signal Processing at RF) program to miniaturize these devices and improve performance metrics. Krishnaswamy’s group was the only one to integrate these non-reciprocal devices on a compact chip and also demonstrate performance metrics that were orders of magnitude superior to prior work. The study was presented in a paper at the IEEE International Solid-State Circuits Conference in February 2020, and published May 4, 2020, in Nature Electronics.

“For these circulators to be used in practical applications, they need to be able to handle watts of power without breaking a sweat,” says Krishnaswamy, whose research focuses on developing integrated electronic technologies for new high-frequency wireless applications. “Our earlier work performed at a rate 25 times lower than this new one — our 2017 device was an exciting scientific curiosity but it was not ready for prime time. Now we’ve figured out how to build these one-way devices in a compact chip, thus enabling them to become small, low cost, and widespread. This will transform all kinds of electronic applications, from VR headsets to 5G cellular networks to quantum computers.”

Traditional “one-way” devices are built using magnetic materials, such as ferrites, but these materials cannot be integrated into modern semiconductor fabrication processes because they are too bulky and expensive. While creating non-reciprocal components without the use of magnetic materials has a long history, advancements in semiconductor technology have brought it to the forefront. Krishnaswamy’s group has been focused on developing time-varying circuits, specifically circuits driven by a clock signal, that have been shown to achieve non-reciprocal responses.

The original discovery was made in 2017, when Krishnaswamy’s PhD student, Negar Reiskarimian, who is now an assistant professor at MIT and co-author of the Nature Electronics study, was experimenting with a new type of circuit called an N-path filter. She was trying to build a different kind of device called a duplexer, which enables simultaneous transmission and reception but at two separate frequencies. In playing around with that circuit, she connected it in a loop and saw this non-reciprocal circulation behavior.

“At first we didn’t believe what we were seeing and were convinced the simulator was broken,” Krishnaswamy says. “But when we took the time to understand it, we realized that this was something new and really big.”

Over the past four years, Krishnaswamy’s group has been primarily focused on the applications of non-reciprocity in wireless applications, such as full-duplex wireless. Now, having developed this promising new compact chip, they are turning their attention to quantum computing. Quantum computers use components such as circulators and isolators to read qubits without disturbing them. Magnetic circulators and isolators are currently used in these cryogenic quantum computers, but they are large in size and expensive, posing one of the bottlenecks to realizing quantum computers with a large number of qubits. Krishnaswamy’s group is looking into using superconducting Josephson Junctions, the same technology used to make the qubit, to realize chip-scale cryogenic circulators that can be directly integrate with qubits, dramatically reducing cost and size.

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Materials provided by Columbia University School of Engineering and Applied Science. Original written by Holly Evarts. Note: Content may be edited for style and length.

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Can API-Driven Technology Help Save the Media?

The digital age has not been kind to media outlets. While the importance of a message, its medium, and knowing how and where to spread it is becoming ever more critical, it doesn’t help that in most cases the media is being held back by old online digital architecture.

Can new technology save media from being trapped by slow, siloed, and expensive traditional systems? The so-called headless CMS (content management system) tears apart the monolithic website architecture from 10 years ago, replacing it with a flexible API-led approach at a far lower cost and a new level of efficiency and flexibility.  This approach enables the same content to be displayed on nearly any device — a website, smartphone, smartwatch, you name it. This represents a big step forward for publishing in efficiency and in lowering costs.

What is the headless CMS?

The headless CMS represents the next step in the ever-evolving strategies and technologies behind publishing on the Internet. A headless setup opens up an incredible level of flexibility, making it simple to publish on any medium (website, smartphone, etc.). The headless CMS is completely customizable using application programming interfaces (APIs) so that content from databases and files can be accessed for display on websites or used by smartphone programs or almost anything including the Internet of Things (IoT) or virtual reality devices. In addition, the headless CMS can be used with the popular front-end JavaScript frameworks (React, Next.js, Node.js) giving developers the freedom to use their favorite design tools. This combination of APIs and headless CMS available as open-source software gives content creators and developers unprecedented easy access to content enabling media publishers to build better digital experiences.

What are the benefits of a headless CMS?

Rather than trying to reshape an outdated architecture, headless CMS solves the legacy problem once and for all by being future-proof by design. New channels for accessing digital content are instantly accessible with an API, key components of the stack are easily replaceable, and scaling is simplified.

This translates into an efficient ecosystem where media publishers have less to worry about, letting the conversation shift from basic maintenance to innovative ideas and experiments on new platforms.

Breaking it down further while keeping things simple, there are four main benefits that come with a headless solution: flexibility, performance, security, and cost.

Infinite Flexibility

When talking about headless CMS, it’s important to remember that everything comes back to the architecture. This isn’t a new form of technology or a killer app, it’s a new way to organize web development.

Relying on nothing but an API turns the entire management structure into a system that works with a universal adapter. It’s as big a change as going from proprietary I/O for every piece of hardware to using a USB for nearly everything. All that’s needed is the right adapter and you can have content wherever you want. The same data can be used and deployed across multiple platforms. Any new device, any new outlet, any new technology can be ready to serve content in minutes. All that’s needed is an API, which gives media publishers great efficiency and flexibility to push their content out.

It’s possible to deliver perfect user experiences using the latest user interfaces. With a headless CMS, customizable front-end displays adapt to whatever people want.

Lightning Fast Performance

The added flexibility that comes with moving away from the coupled stack of the monolithic CMS brings with it a nice boost to performance as well. With headless CMS, only the most relevant parts of the stack are ever running when a user makes a request, speeding the whole process by removing the number of steps.

Those benefits are amplified by the use of static websites to quickly serve content rather than rebuilding everything from scratch for every request. To paint a clearer picture, imagine how a static site generator (Gatsby, for example) gathers all the data it needs to build a website from an API created by a headless CMS. Once that site is built, there is no more need to gather the data, ensuring access to the website for all future users, reducing the number of API requests, and once again speeding up the entire process.

The cherry on top is that because of that structural change, even if the API is down and not working, the website or app will continue to function normally since it was already successfully built.

Built-In Security

Many of the very same aspects that allow for faster performance and allow for infinite flexibility also provide better security. All components operate independently and only the most relevant parts of the stack are activated at any given time. By separating content creation from content delivery, much less is exposed publicly. The always-available static deployment that comes with a headless CMS reduces the overall surface area attack points for malicious actors. Most of the stack remains hidden making it less vulnerable to hackers.

Low Cost

The last benefit may be hard to believe, but a direct result of shifting to a headless CMS is lower cost. In fact, all the benefits listed above come with an intrinsic reduction in maintenance and management. Not to mention, there are headless CMS available as free, open-source software.

Breaking content silos allows for simpler coordination, allowing more time for the creation of effective and impactful content across all devices with less time spent struggling to manage specialized teams with different needs limited by legacy systems.

For the exact same reasons, it instantly becomes easier to target new audiences and new devices with a headless CMS. Limitations caused by building specific implementations for every emerging technology are completely eliminated. Content lives wherever end-users, customers, consumers, and visitors want to access it.

Unleash media content with a headless CMS

A headless CMS is the easy way to overcome the issues tied to proprietary, restrictive, outdated, and expensive content management, which are so vital to media publishers. It’s time for media publishers to step away from the historical baggage of their current digital publishing systems and move into the immeasurable potential of the headless CMS as the obvious path for the future to deliver impactful content.

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Author: <a href="">PBurgy</a>


First-ever comprehensive geologic map of the moon

Have you ever wondered what kind of rocks make up those bright and dark splotches on the moon? Well, the USGS has just released a new authoritative map to help explain the 4.5-billion-year-old history of our nearest neighbor in space.

For the first time, the entire lunar surface has been completely mapped and uniformly classified by scientists from the USGS, in collaboration with NASA and the Lunar Planetary Institute.

The lunar map, called the “Unified Geologic Map of the Moon,” will serve as the definitive blueprint of the moon’s surface geology for future human missions and will be invaluable for the international scientific community, educators and the public-at-large. The digital map is available online now and shows the moon’s geology in incredible detail (1:5,000,000 scale).

“People have always been fascinated by the moon and when we might return,” said current USGS Director and former NASA astronaut Jim Reilly. “So, it’s wonderful to see USGS create a resource that can help NASA with their planning for future missions.”

To create the new digital map, scientists used information from six Apollo-era regional maps along with updated information from recent satellite missions to the moon. The existing historical maps were redrawn to align them with the modern data sets, thus preserving previous observations and interpretations. Along with merging new and old data, USGS researchers also developed a unified description of the stratigraphy, or rock layers, of the moon. This resolved issues from previous maps where rock names, descriptions and ages were sometimes inconsistent.

“This map is a culmination of a decades-long project,” said Corey Fortezzo, USGS geologist and lead author. “It provides vital information for new scientific studies by connecting the exploration of specific sites on the moon with the rest of the lunar surface.”

Elevation data for the moon’s equatorial region came from stereo observations collected by the Terrain Camera on the recent SELENE (Selenological and Engineering Explorer) mission led by JAXA, the Japan Aerospace Exploration Agency. Topography for the north and south poles was supplemented with NASA’s Lunar Orbiter Laser Altimeter data.

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Discovery points to origin of mysterious ultraviolet radiation

Billions of lightyears away, gigantic clouds of hydrogen gas produce a special kind of radiation, a type of ultraviolet light known as Lyman-alpha emissions. The enormous clouds emitting the light are Lyman-alpha blobs (LABs). LABs are several times larger than our Milky Way galaxy, yet were only discovered 20 years ago. An extremely powerful energy source is necessary to produce this radiation — think the energy output equivalent of billions of our sun — but scientists debate what that energy source could be.

A new study that published on March 9 in Nature Astronomy provides evidence that the energy source is at the center of star-forming galaxies, around which the LABs exist.

The study focuses on Lyman-alpha blob 6 (LAB-6) located more than 18 billion light years away in the direction of constellation Grus. The collaborative team discovered a unique feature of LAB-6 — its hydrogen gas appeared to fall inwards on itself. LAB-6 is the first LAB with strong evidence of this so-called infalling gas signature. The infalling gas was low in abundance of metallic elements, suggesting that the LAB’s infalling hydrogen gas originated in the intergalactic medium, rather than from the star-forming galaxy itself.

The amount of infalling gas is too low to power the observed Lyman-alpha emission. The findings provide evidence that the central star-forming galaxy is the primary energy source responsible for Lyman-alpha emission. They also pose new questions about the structure of the LABs.

“This gives us a mystery. We expect there should be infalling gas around star-forming galaxies — they need gas for materials,” said Zheng Zheng, associate professor of physics and astronomy at the University of Utah and co-author of the study. Zheng joined the effort of analyzing the data and led the theoretical interpretation with U graduate student Shiyu Nie. “But this seems to be the only Lyman-alpha blob with gas infalling. Why is this so rare?”

The authors used the Very Large Telescope (VLT) at the European Southern Observatory (ESO) and the Atacama Large Millimeter/Submillimeter Array (ALMA) to obtain the data. Lead author Yiping Ao of Purple Mountain Observatory, Chinese Academy of Sciences first observed the LAB-6 system over a decade ago. He knew there was something special about the system even then, based on the extreme size of its hydrogen gas blob. He jumped at the chance to look more closely.

“Luckily, we were able to obtain the data necessary to capture the molecular makeup from ALMA, pinning down the velocity of the galaxy,” he said. “The optical telescope VLT from ESO gave us the important spectral light profile of Lyman-alpha emission.”

Hydrogen’s light reveals its secret

The universe is filled with hydrogen. The hydrogen electron orbits the atom’s nucleus on different energy levels. When a neutral hydrogen atom gets blasted with energy, the electron can be boosted to a larger orbit with a higher energy level. Then the electron can jump from one orbit level to another, which produces a photon. When the electron moves to the inner-most orbit from the orbit directly adjacent, it emits a photon with a particular wavelength in the ultraviolet spectrum, called a Lyman-alpha emission. A powerful energy source is required to energize hydrogen enough to produce the Lyman-alpha emission.

The authors discovered the infalling gas feature by analyzing the kinematics of the Lyman-alpha emissions. After the Lyman-alpha photon is emitted, it encounters an environment filled with hydrogen atoms. It crashes into these atoms many times, like a ball moving in a pinball machine, before escaping the environment. This exit makes the emission extend outward over great distances.

All of this bouncing around not only changes the light wave’s direction, but also its frequency, as the motion of gas causes a Doppler effect. When gas is outflowing, the Lyman-alpha emission shifts into the longer, redder wavelength. The opposite occurs when gas is inflowing — the Lyman-alpha emission’s wavelength appears to get shorter, shifting it into a bluer spectrum.

The authors of this paper used the ALMA observation to locate the expected wavelength of the Lyman-alpha emission from the Earth’s prospective, if there were no bouncing effect for the Lyman-alpha photons. With the VLT observation, they found that Lyman-alpha emission from this blob shifts into longer wavelength, implying gas inflow. They used models to analyze the spectrum data and study the kinematics of hydrogen gas.

The infalling gas narrows down Lyman-alpha radiation’s origin

LABs are associated with gigantic galaxies that are forming stars at a rate of hundreds to thousands of solar mass per year. Giant halos of Lyman-alpha emissions surround these galaxies, forming the Lyman-alpha gas blobs hundreds of thousands of light years across with power equivalent of about 10 billion suns. The movement within the gas blobs can tell you something about the state of the galaxy.

Infalling gas can originate several different ways. It could be the second stage of a galactic fountain — if massive stars die, they explode and push gas outward, which later falls inwards. Another option is a cold stream — there are filaments of hydrogen floating between celestial objects that can be pulled into the center of potential well, creating the infalling gas feature.

The authors’ model suggests that the infalling gas in this LAB comes from the latter scenario. They analyzed the shape of the Lyman-alpha light profile, which indicates very little metallic dust. In astronomy, metals are anything heavier than helium. Stars produce all of the heavy elements in the universe — when they explode, they produce metallic elements and spread them across intergalactic space.

“If the gas had come from this galaxy, you should see more metals. But this one, there weren’t a lot of metals,” said Zheng. “The indication is that the gas isn’t contaminated with elements from this star formation.”

Additionally, their model indicates that the surrounding gas only produces the energy power equivalent of two solar masses per year, much too low for the amount for the observed Lyman-alpha emission.

The findings provide strong evidence that the star-forming galaxy is the major contributor of the Lyman-alpha emission, while the infalling gas acts to shape its spectral profile. However, it doesn’t completely answer the question.

“There may still be other possibilities,” said Ao. “If the galaxy has a super massive black hole in the center, it can emit energetic photons that could travel far enough to produce the emission.”

In future studies, the authors want to tease apart the complicated gas dynamics to figure out why infalling gas is rare for LABs. The inflowing gas could depend on the orientation of the system, for example. They also want to build more realistic models to understand the movements of the Lyman-alpha emission photons as they crash into atoms.

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IEEE Spectrum

New Nonvolatile Memories Shrink Circuits That Search Fast

The kind of memory most people are familiar with returns data when given an address for that data. Content addressable memory (CAM) does the reverse: When given a set of data, it returns the address—typically in a single clock cycle—of where to find it. That ability, so useful in network routers and other systems that require a lot of lookups, is now getting a chance in new kinds of data-intensive tasks such as pattern matching and accelerating neural networks, as well as for doing logic operations in the memory itself.

IEEE Spectrum

Chicken Droppings Can Make Graphene More Catalytic

Practically any kind of crap can boost graphene’s properties as a catalyst—even chicken droppings, say the authors of a new tongue-in-cheek study.

Graphene is often hailed as a wonder material—flexible, transparent, light, strong, and electrically and thermally conductive. Such qualities have led researchers worldwide to consider weaving these one-atom-thick sheets of carbon into advanced devices. Scientists have also explored graphene’s properties as a catalyst for the kinds of oxygen reduction reactions often used in fuel cells and the hydrogen evolution reactions used to split apart water molecules to generate hydrogen fuel.

To further enhance graphene’s catalytic properties, researchers have tried doping it with a variety of elements. Seemingly all such studies have claimed graphene’s catalytic abilities improved, regardless of whether the doping materials had contrasting properties with each other. This is “contrary to what any material scientist might expect,” says Martin Pumera, a materials scientist at the University of Chemistry and Technology in Prague.