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Archive for the ‘physics’ category: Page 3

Oct 29, 2022

A Möbius Strip for Light

Posted by in categories: materials, physics

A ring-shaped waveguide with a particular pattern of notches can force a light wave to make two round trips before completing an integer number of wave cycles.

Light can travel along a closed path inside a ring of glass or similar material, reflecting repeatedly from the interior surface. Although such closed-loop waves generally have integer values of angular momentum, researchers using a small gear-shaped ring have now demonstrated an ability to generate similar waves with unusual fractional values of angular momentum [1]. As in a Möbius strip, the waves must make two round trips to return to their initial configuration. The ability to tune the angular momentum in this way could give researchers more precise control of light in advanced devices such as single-photon emitters.

Physicists refer to the closed-loop waves as whispering gallery modes, named after an acoustic effect in round rooms, where sounds reflect multiple times off the walls. Ordinarily, a wave of this kind moves around a single closed loop before retracing its earlier path. The phase of the electric field associated with the wave front must go through an integer number M of cycles in making one loop. Technically, this condition also implies that the photons associated with the wave will carry an integer number M units of angular momentum.

Oct 29, 2022

Astrophysicists make observations consistent with the predictions of an alternative theory of gravity

Posted by in category: physics

An international team of astrophysicists has made a puzzling discovery while analyzing certain star clusters. The finding challenges Newton’s laws of gravity, the researchers write in their publication. Instead, the observations are consistent with the predictions of an alternative theory of gravity. However, this is controversial among experts. The results have now been published in the Monthly Notices of the Royal Astronomical Society.

In their work, the researchers investigated open star clusters. These are formed when thousands of stars are born within a short time in a huge gas cloud. As they “ignite,” the galactic newcomers blow away the remnants of the gas cloud. In the process, the cluster expands considerably. This creates a loose formation of several dozen to several thousand stars. The weak gravitational forces acting between them hold the cluster together.

“In most cases, open star clusters survive only a few hundred million years before they dissolve,” explains Prof. Dr. Pavel Kroupa of the Helmholtz Institute of Radiation and Nuclear Physics at the University of Bonn. In the process, they regularly lose stars, which accumulate in two so-called “tidal tails.” One of these tails is pulled behind the cluster as it travels through space. The other, in contrast, takes the lead like a spearhead.

Oct 28, 2022

Brightest-Ever Space Explosion Reveals Possible Hints of Dark Matter

Posted by in categories: cosmology, mobile phones, physics

O.o!!


On Sunday, October 9, Judith Racusin was 35,000 feet in the air, en route to a high-energy astrophysics conference, when the biggest cosmic explosion in history took place. “I landed, looked at my phone, and had dozens of messages,” said Racusin, an astrophysicist at NASA’s Goddard Space Flight Center in Maryland. “It was really exceptional.”

The explosion was a long gamma-ray burst, a cosmic event where a massive dying star unleashes powerful jets of energy as it collapses into a black hole or neutron star. This particular burst was so bright that it oversaturated the Fermi Gamma-ray Space Telescope, an orbiting NASA telescope designed in part to observe such events. “There were so many photons per second that they couldn’t keep up,” said Andrew Levan, an astrophysicist at Radboud University in the Netherlands. The burst even appears to have caused Earth’s ionosphere, the upper layer of Earth’s atmosphere, to swell in size for several hours. “The fact you can change Earth’s ionosphere from an object halfway across the universe is pretty incredible,” said Doug Welch, an astronomer at McMaster University in Canada.

Continue reading “Brightest-Ever Space Explosion Reveals Possible Hints of Dark Matter” »

Oct 28, 2022

2D nanoconfinement strategy enhances oxygen evolution performances

Posted by in categories: chemistry, energy, engineering, physics, sustainability

Prof. Zhang Tao’s group at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. Hou Yang from Zhejiang University and Prof. Xiao Jianping from the Dalian Institute of Chemical Physics of CAS, proposed a novel two-dimensional (2D) nanoconfinement strategy to strongly enhance the oxygen evolution reaction (OER) activity of low-conductivity metal-organic frameworks (MOFs). Results were published in Nature Communications.

The development of high-efficiency electrocatalysts for the electrochemical conversion of water to generate environmentally friendly and sustainable hydrogen energy has drawn tremendous attention for decades.

Despite the crucial role the OER plays in water splitting, OER at the anode requires a relatively high thermodynamic potential to accelerate water splitting kinetics. Thanks to the large surface area, tunable porosity, diverse compositions and metal centers, MOFs have emerged as promising candidates for efficient OER electrocatalysts. However, the intrinsically poor conductivity of the most MOFs seriously impede their .

Oct 27, 2022

Research team proposes unclonable, invisible machine vision markers using cholesteric spherical reflectors

Posted by in categories: augmented reality, blockchains, economics, mobile phones, physics, robotics/AI, wearables

Over the last three decades, the digital world that we access through smartphones and computers has grown so rich and detailed that much of our physical world has a corresponding life in this digital reality. Today, the physical and digital realities are on a steady course to merging, as robots, Augmented Reality (AR) and wearable digital devices enter our physical world, and physical items get their digital twin computer representations in the digital world.

These digital twins can be uniquely identified and protected from manipulation thanks to crypto technologies like blockchains. The trust that these technologies provide is extremely powerful, helping to fight counterfeiting, increase supply chain transparency, and enable the circular economy. However, a weak point is that there is no versatile and generally applicable identifier of physical items that is as trustworthy as a blockchain. This breaks the connection between the physical and digital twins and therefore limits the potential of technical solutions.

In a new paper published in Light: Science & Applications, an interdisciplinary team of scientists led by Professors Jan Lagerwall (physics) and Holger Voos (robotics) from the University of Luxembourg, Luxembourg, and Prof. Mathew Schwartz (architecture, construction of the built environment) from the New Jersey Institute of Technology, U.S., propose an innovative solution to this problem where physical items are given unique and unclonable fingerprints realized using cholesteric spherical reflectors, or CSRs for short.

Oct 27, 2022

Listening to Equation-of-State Changes

Posted by in categories: information science, physics, space

Simulations indicate that postmerger gravitational waves from coalescing neutron stars could allow researchers to hear the phase transitions between exotic states of matter.

Oct 27, 2022

Toward next‐generation lava flow forecasting: Development of a fast, physics‐based lava propagation model

Posted by in categories: climatology, physics

When a volcanic eruption occurs in an inhabited area, rapid and accurate lava flow forecasts can save lives and reduce infrastructure and property losses. To ensure that current lava forecasting models can provide outputs fast enough to be useful in practice, they unfortunately must incorporate physical simplifications that limit their accuracy.

To aid evacuation plans, forecast models must predict a ’s speed, direction, and extent. These attributes are intimately connected to how the lava solidifies as it cools. Yet to achieve real-time speed, most assume that a flow has a uniform temperature. This is a major simplification that directly influences modeled rates of cooling; generally, are much cooler at their boundaries, where they are in contact with air or the ground, than they are internally.

Aiming to strike a better compromise between speed and realism, David Hyman and a team developed a 2D, physics-based lava flow model called Lava2d. They extended the traditional, vertically averaged treatment of a lava packet by considering it as three distinct regions: the portion near the lava-air boundary, the portion near the lava-ground boundary, and the fluidlike central core. The top and bottom regions of a modeled flow cool based on the physics of heat transfer to the air and ground, while the temperature in the center remains uniform, as in prior approaches. This setup enables the model to account for a without requiring a computationally expensive 3D approach.

Oct 27, 2022

Machine learning could vastly speed up the search for new metals

Posted by in categories: chemistry, physics, robotics/AI

The findings could help pave the way for greater use of machine learning in materials science, a field that still relies heavily on laboratory experimentation. Also, the technique of using machine learning to make predictions that are then checked in the lab could be adapted for discovery in other fields, such as chemistry and physics, say experts in materials science.

To understand why it’s a significant development, it’s worth looking at the traditional way new compounds are usually created, says Michael Titus, an assistant professor of materials engineering at Purdue University, who was not involved in the research. The process of tinkering in the lab is painstaking and inefficient.

Oct 26, 2022

Researchers compress light 12 times below the diffraction limit in a dielectric material

Posted by in categories: nanotechnology, physics

Until recently, it was widely believed among physicists that it was impossible to compress light below the so-called diffraction limit (see below), except when using metal nanoparticles, which unfortunately also absorb light. It therefore seemed impossible to compress light strongly in dielectric materials such as silicon, which are key materials in information technologies and come with the important advantage that they do not absorb light.

Interestingly, it was shown theoretically in 2006 that the diffraction limit also does not apply to dielectrics. Still, no one has succeeded in showing this in the , simply because no one has been able to build the necessary nanostructures until now.

A research team from DTU has successfully designed and built a structure, a so-called dielectric nanocavity, which concentrates light in a volume 12 times below the diffraction limit. The result is groundbreaking in optical research and has just been published in Nature Communications.

Oct 25, 2022

SpaceX to launch Europe’s next deep space telescope, first asteroid orbiter

Posted by in categories: physics, space travel

On October 17th, a NASA official speaking at an Astrophysics Advisory Committee meeting revealed that the European Space Agency (ESA) had begun “exploring options” and studying the feasibility of launching the Euclid near-infrared space telescope on SpaceX’s Falcon 9 rocket.

In a major upset, director Josef Aschbacher confirmed less than three days later that ESA will contract with SpaceX to launch the Euclid telescope and Hera, a multi-spacecraft mission to a near-Earth asteroid, after all domestic alternatives fell through.

The European Union and, by proxy, ESA, are infamously insular and parochial about rocket launch services. That attitude was largely cultivated by ESA and the French company Arianespace’s success in the international commercial launch market in the 1980s, 1990s, and 2000s – a hard-fought position that all parties eventually seemed to take for granted. When that golden era slammed headfirst into the brick wall erected by SpaceX in the mid-2010s, Arianespace found itself facing a truly threatening competitor for the first time in 15+ years.

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