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Category: materials – Page 93

Rice University materials scientists developed a fast, low-cost, scalable method to make covalent organic frameworks (COFs). Credit: Photo by Gustavo Raskosky/Rice University.

Materials scientists at Rice University have created an efficient, affordable, and scalable technique for producing covalent organic frameworks (COFs). These crystalline polymers are notable for their adjustable molecular structure, extensive surface area, and porosity, making them potentially valuable in areas like energy applications, semiconductor devices, sensors, filtration systems, and drug delivery.

“What makes these structures so special is that they are polymers but they arrange themselves in an ordered, repeating structure that makes it a crystal,” said Jeremy Daum, a Rice doctoral student and lead author of a study published in ACS Nano. “These structures look a bit like chicken wire ⎯ they’re hexagonal lattices that repeat themselves on a two-dimensional plane, and then they stack on top of themselves, and that’s how you get a layered 2D material.”

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Some of the finest, smallest details in the universe – the gaps between elongated groups of stars – may soon help astronomers reveal dark matter in greater detail than ever before. After NASA’s Nancy Grace Roman Space Telescope launches, by May 2027, researchers will use its images to explore what exists between looping tendrils of stars that are pulled from globular clusters. Specifically, they will focus on the tidal streams from globular clusters that orbit our neighboring Andromeda galaxy. Their aim is to pinpoint a greater number of examples of these tidal streams, examine gaps between the stars, and ideally determine concrete properties of dark matter.

Globular cluster streams are like ribbons fluttering in the cosmos, both leading and trailing the globular clusters where they originated along their orbits. Their lengths in our Milky Way galaxy vary wildly. Very short stellar streams are relatively young, while those that completely wrap around a galaxy may be almost as old as the universe. A stream that is fully wrapped around the Andromeda galaxy could be more than 300,000 light-years long but less than 3,000 light-years wide.

With Roman, astronomers will be able to search nearby galaxies for globular cluster stellar streams for the first time. Roman’s Wide Field Instrument has 18 detectors that will produce images 200 times the size of the Hubble Space Telescope’s near-infrared camera – at a slightly greater resolution.

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Researchers have demonstrated a mirror-based neutron interferometer that should be more sensitive to beyond-standard-model particle interactions than previous instruments.

Some theories of beyond-standard-model physics predict that neutrons passing close to an atomic nucleus will experience exotic interactions with the particles in that nucleus. To try to spot these interactions, physicists use a neutron interferometer, a device that splits and then recombines a neutron beam. If a currently unknown particle interaction affects one branch of the split beam as it passes through a material, the signature should show up in the interference pattern that forms when the two beams come back together. Takuhiro Fujiie at Nagoya University, Japan, and colleagues have now demonstrated a new neutron interferometer that promises greater sensitivity to beyond-standard-model physics [1].

In a conventional neutron interferometer, components made of crystalline silicon manipulate the neutron beam. Such interferometers only work for neutron beams that have wavelengths between 0.19 and 0.44 nm because of the spacings between crystalline silicon’s atoms. In the new instrument, neutron mirrors composed of alternating layers of nickel and titanium manipulate the neutron beam. The spacing of the layers determines the wavelength reflected and can be tuned to make mirrors that work for a wider range of neutron-beam wavelengths—including longer wavelengths that offer greater measurement sensitivity.

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“The Stardust samples, microscopic grains from a body less than two miles wide, contain a record of the deep past covering billions of miles,” said Dr. Ryan Ogliore. “After 18 years of interrogating this comet, we have a much better view of the solar system’s dynamic formative years.”

What can samples collected from a comet almost 20 years ago tell us about the history of comets and our solar system? This is what a recent study published in Geochemistry hopes to address as a researcher from the Washington University in St. Louis (WUSTL) analyzed samples from Comet 81P/Wild 2 that were returned to Earth almost exactly 18 years ago today. This study holds the potential to help scientists not only gain greater insights into the origin and history of comets, but of our solar system, as well.

Image of the Stardust sample return capsule being retrieved inside a protective covering after it was collected from its landing site at the U.S. Air Force Utah Test and Training Range in January 2006. (Credit: NASA)

While Comet 81P/Wild 2 currently orbits in the main asteroid belt between Mars and Jupiter, scientists have long hypothesized that the comet formed much farther out, possibly beyond the orbit of Neptune. Therefore, they interpreted that any samples collected from the comet would contain material from the interstellar medium before the formation of the solar system. However, the samples that returned to Earth from NASA’s Stardust mission have revealed material comprised of a variety of events that occurred during the early age of the solar system, as opposed to strictly before the solar system formed.

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Just like a book can’t be judged by its cover, a material can’t always be judged by its surface. But, for an elusive conjectured class of materials, physicists have now shown that the surface previously thought to be “featureless” holds an unmistakable signature that could lead to the first definitive observation.

Higher-order , or HOTIs, have attracted attention for their ability to conduct electricity along one-dimensional lines on their surfaces, but this property is quite difficult to experimentally distinguish from other effects. By instead studying the interiors of these materials from a , a team of physicists has identified a signature that is unique to HOTIs that can determine how light reflects from their surfaces.

As the team reports in the journal Nature Communications, this property could be used to experimentally confirm the existence of such topological states in real materials.

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Just like humans, plants also communicate with each other as soon as any danger or attack is detected in their neighbourhood. Scientists know about this phenomenon since the 1980s, having identified at least 80 species who act in their defence in crisis situations. However, it was still shrouded in mystery as to how exactly plants receive such danger signals from their neighbours.

Now, a team of Japanese scientists has not just solved this puzzle but also filmed the communication among plants in an amazing video. In a study published in Nature Communications, molecular biologists at Saitama University in Japan, Yuri Aratani and Takuya Uemura, demonstrated how these plants behave upon detecting danger.

To conduct the experiment, scientists set off caterpillars on leaves cut from tomato plants and a commonly used weed called Arabidopsis thaliana. To better analyse its impact on the neighbouring plant, the compounds were concentrated in a plastic bottle and pumped onto the recipient plant at a constant rate.

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Rishi Sunak needs to decide whether he wants to back the UK’s creative industries or gamble everything on an artificial intelligence boom, the chief executive of Getty Images has said.

Craig Peters, who has led the image library since 2019, spoke out amid growing anger from the creative and media sector at the harvesting of their material for “training data” for AI companies. His company is suing a number of AI image generators in the UK and US for copyright infringement.

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