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Category: physics

Researchers from the Institute of Solid State Physics, the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, in collaboration with Southwest Jiaotong University, have combined high-pressure electrical transport experiments, high-pressure Raman spectroscopy, and first-principles calculations to reveal the structural phase transition behavior of hafnium oxide (HfO2) under high pressure and its evolution mechanism in electrical properties.

The paper is published in the journal Physical Review B.

“This study resolves the previous controversies regarding the phase transitions of HfO2 in the low-pressure region,” said Pan Xiaomei, a member of the team.

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Every time the temperature drops, a cloud passes overhead, or the sun sets, a plant makes a choice: Keep its microscopic pores, called stomata, open to absorb carbon dioxide and continue photosynthesizing or close them to protect its precious stores of water. That capacity to open and close pores requires the plant to respond to subtle environmental changes by adjusting the pressure within the cells of the stomata—a complex ability that plants evolved over hundreds of millions of years.

An interdisciplinary team of biologists, physicists, and engineers, led by researchers at the Yale School of the Environment, has developed a method to observe those pressure changes. The new approach, detailed in a study published in PNAS, vastly expands the rate at which—and the number of species from which—scientists can take measurements, opening up new possibilities for research on and physiology with valuable applications for improving water efficiency, the researchers said.

“Almost every single land plant is using this principle of internal pressure in order to grow, reproduce, and do everything a plant does, but we previously had basically no access to this measurement,” said Craig Brodersen, the Howard and Maryam Newman Professor of Plant Physiological Ecology and the lead author of the study.

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Why would anyone need this level of wavelength detail in an image? There are many reasons. Car manufacturers want to predict exactly how paint will look under different lighting. Scientists use spectral imaging to identify materials by their unique light signatures. And rendering specialists need it to accurately simulate real-world optical effects like dispersion (rainbows from prisms, for example) and fluorescence.

For instance, past Ars Technica coverage has highlighted how astronomers analyzed spectral emission lines from a gamma-ray burst to identify chemicals in the explosion, how physicists reconstructed original colors in pioneering 19th century photographs, and how multispectral imaging revealed hidden, centuries-old text and annotations on medieval manuscripts like the Voynich Manuscript, sometimes even uncovering the identities of past readers or scribes through faint surface etchings.

The current standard format for storing this kind of data, OpenEXR, wasn’t designed with these massive spectral requirements in mind. Even with built-in lossless compression methods like ZIP, the files remain unwieldy for practical work as these methods struggle with the large number of spectral channels.

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Astrophysicists at the University of Colorado’s JILA, National Institute of Science and Technology, have conducted an experiment to produce benzene the way theories have predicted it is produced in interstellar space and found it did not produce any benzene. The research by G. S. Kocheril, C. Zagorec-Marks and H. J. Lewandowski is published in the journal Nature Astronomy.

Research efforts in the 1990s led to theories suggesting that ion-molecule collisions could be one of the main ways that interstellar forms. Such theories are important for space research because it is believed that benzene is a precursor to the formation of interstellar , which are believed to hold cosmic carbon, which is important for many reasons but mainly because of the role it might have played in the development of carbon-based lifeforms.

Testing of theories that lead to the creation of benzene in has not been done before because of the difficulty in creating the conditions that exist in such an environment. In their paper, and during a speech at a recent symposium, the group stated that they had the equipment necessary to carry out such an experiment in their lab at JILA.

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In 1994 Miguel Alcubierre was able to construct a valid solution to the equations of general relativity that enable a warp drive. But now we need to tackle the rest of relativity: How do we arrange matter and energy to make that particular configuration of spacetime possible?

Unfortunately for warp drives, that’s when we start running into trouble. In fact, right away, we run into three troubles. And these three troubles are called the energy conditions. Now, before I describe the energy conditions, I need to make a disclaimer. What I’m about to say are not iron laws of physics.

They are instead reasonable guesses as to how nature makes sense. General relativity is a machine. You put in various configurations of spacetime, various arrangements of matter and energy. You turn the handle and you learn how gravity works. General relativity on its own doesn’t tell you what’s real and what’s not.

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How gravity causes a perfectly spherical ball to roll down an inclined plane is part of the elementary school physics canon. But the world is messier than a textbook.

Scientists in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have sought to quantitatively describe the much more complex rolling physics of real-world objects. Led by L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, Physics, and Organismic and Evolutionary Biology in SEAS and FAS, they combined theory, simulations, and experiments to understand what happens when an imperfect, spherical object is placed on an inclined plane.

Published in Proceedings of the National Academy of Sciences, the research, which was inspired by nothing more than curiosity about the everyday world, could provide fundamental insights into anything that involves irregular objects that roll, from nanoscale cellular transport to robotics.

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Professor Ariando and Dr. Stephen Lin Er Chow from the National University of Singapore (NUS) Department of Physics have designed and synthesized a groundbreaking new material—a copper-free superconducting oxide—capable of superconducting at approximately 40 Kelvin (K), or about minus 233°C, under ambient pressure.

Nearly four decades after the discovery of copper oxide superconductivity, which earned the 1987 Nobel Prize in Physics, the NUS researchers have now identified another high-temperature superconducting oxide that expands the understanding of unconventional superconductivity beyond copper oxides.

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Using NASA’s Chandra X-ray observatory, astronomers have observed a massive and hot galaxy cluster known as PLCKG287.0+32.9 (or PLCKG287 for short). Results of the observational campaign, presented March 17 on the arXiv pre-print server, deliver important insights into the morphological and thermodynamical properties of this cluster.

Galaxy clusters contain up to thousands of galaxies bound together by gravity. They generally form as a result of mergers and grow by accreting sub-clusters. These processes provide an excellent opportunity to study matter in conditions that cannot be explored in laboratories on Earth. In particular, merging could help us better understand the physics of shock and cold fronts seen in the diffuse intra-cluster medium, the cosmic ray acceleration in clusters, and the self-interaction properties of dark matter.

PLCKG287, also known as PSZ2 G286.98+32.90, is a galaxy cluster at a redshift of 0.38, with a mass of about 1.37 quadrillion solar masses and a temperature of 13 keV. The cluster has an X-ray luminosity in the 2–10 keV band at a level of 1.7 quattuordecillion erg/s.

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