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Category: physics

Metamaterials, which are engineered to have properties not found in nature, have long been developed and studied because of their unique features and exciting applications. However, the physics behind their thermal emission properties have remained unclear to researchers—until now.

In a paper published in Physical Review Letters, Sheng Shen, an associate professor in Carnegie Mellon’s department of mechanical engineering, and his student Jiayu Li, a Ph.D. candidate, have created a new scale law to describe the thermal emission from metasurfaces and metamaterials.

“With this new scale law uncovering the underlying physics behind the collective thermal emission behavior of metamaterials, researchers could easily utilize existing design and optimization tools to achieve desired thermal emission properties from metamaterials, instead of blindly searching for the best solution through mapping the entire design space,” Li said.

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In the summer of 2010, I had the opportunity to be part of the team that designed and built the first passive freezer that we’d ever heard of. The idea was simple, we create a well-insulated room and stack several thousand 2-liter bottles full of salt water along the walls. In the winter, we open hatches in the ceiling and everything freezes. At the end of the winter, we close the hatches and it stays at about 25°F for the whole year.

The team of students, led by physics teacher Tom Tailer ran some calculations to make sure the physics added up and calculated that we needed about 3000 bottles and about 18 inches of foam insulation on the walls and ceiling for good performance. We built the structure and insulated it using waste styrofoam, ground-up using a modified leaf shredder.

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O,.o circa 2012.

An apparatus or structure is proposed for generating high-frequency gravitational waves (HFGWs) between pairs of force–producing elements by means of the simultaneous production of a third time derivative of mass motion of the pair of force–producing elements. The elements are configured as a cylindrical array in the proposed structure and are activated by a radiation wavefront moving along the axis of symmetry of the array. The force-producing elements can be micro-electromechanical systems or MEMS resonators such as film-bulk acoustic resonators or FBARs. A preferred cylindrical array is in the form of a double helix and the activating radiation can be electromagnetic as generated by microwave transmitters such as Magnetrons. As the activating radiation wavefront moves along the axis of the structure it simultaneously activates force elements on opposite sides of the structure and thereby generates a gravitational wave between the pair of force elements. It is also indicated that the Earth is completely transparent to the HFGWs. Thus a sensitive HFGW detector, such as the Li-Baker under development by the Chinese, can sense the generated HFGW at an Earth-diameter distance and could, in theory, be a means for implementing transglobal HFGW communications.

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The Newtonian laws of physics explain the behavior of objects in the everyday physical world, such as an apple falling from a tree. For hundreds of years Newton provided a complete answer until the work of Einstein introduced the concept of relativity. The discovery of relativity did not suddenly prove Newton wrong, relativistic corrections are only required at speeds above about 67 million mph. Instead, improving technology allowed both more detailed observations and techniques for analysis that then required explanation. While most of the consequences of a Newtonian model are intuitive, much of relativity is not and is only approachable though complex equations, modeling, and highly simplified examples.

In this issue, Korman et al.1 provide data from a model of the second gas effect on arterial partial pressures of volatile anesthetic agents. Most readers might wonder what this information adds, some will struggle to remember what the second gas effect is, and others will query the value of modeling rather than “real data.” This editorial attempts to address these questions.

The second gas effect2 is a consequence of the concentration effect3 where a “first gas” that is soluble in plasma, such as nitrous oxide, moves rapidly from the lungs to plasma. This increases the alveolar concentration and hence rate of uptake into plasma of the “second gas.” The second gas is typically a volatile anesthetic, but oxygen also behaves as a second gas.4 Although we frequently talk of inhalational kinetics as a single process, there are multiple steps between dialing up a concentration and the consequent change in effect. The key steps are transfer from the breathing circuit to alveolar gas, from the alveoli to plasma, and then from plasma to the “effect-site.” Separating the two steps between breathing circuit and plasma helps us understand both the second gas effect and the message underlying the paper by Korman et al.1

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A key challenge to capturing and controlling fusion energy on Earth is maintaining the stability of plasma—the electrically charged gas that fuels fusion reactions—and keeping it millions of degrees hot to launch and maintain fusion reactions. This challenge requires controlling magnetic islands, bubble-like structures that form in the plasma in doughnut-shaped tokamak fusion facilities. These islands can grow, cool the plasma and trigger disruptions—the sudden release of energy stored in the plasma—that can halt fusion reactions and seriously damage the fusion facilities that house them.

Improved island control

Research by scientists at Princeton University and at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) points toward improved control of the troublesome magnetic islands in ITER, the international tokamak under construction in France, and other future facilities that cannot allow large disruptions. “This research could open the door to improved control schemes previously deemed unobtainable,” said Eduardo Rodriguez, a graduate student in the Princeton Program in Plasma Physics and first author of a paper in Physics of Plasmas that reports the findings.

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For most of the 20th century, astronomers have scoured the skies for supernovae—the explosive deaths of massive stars—and their remnants in search of clues about the progenitor, the mechanisms that caused it to explode, and the heavy elements created in the process. In fact, these events create most of the cosmic elements that go on to form new stars, galaxies, and life.

Because no one can actually see a supernova up close, researchers rely on to give them insights into the physics that ignites and drives the event. Now for the first time ever, an international team of astrophysicists simulated the three-dimensional (3D) physics of superluminous supernovae—which are about a hundred times more luminous than typical supernovae. They achieved this milestone using Lawrence Berkeley National Laboratory’s (Berkeley Lab’s) CASTRO code and supercomputers at the National Energy Research Scientific Computing Center (NERSC). A paper describing their work was published in Astrophysical Journal.

Astronomers have found that these superluminous events occur when a magnetar—the rapidly spinning corpse of a massive star whose magnetic field is trillions of times stronger than Earth’s—is in the center of a young supernova. Radiation released by the magnetar is what amplifies the supernova’s luminosity. But to understand how this happens, researchers need multidimensional simulations.

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Scientists believe the world will see it’s first working thermonuclear fusion reactor by the year 2025. That’s a tall order in short form, especially when you consider that fusion has been “almost here” for nearly a century.

Fusion reactors – not to be confused with common fission reactors – are the holiest of Grails when it comes to physics achievements. According to most experts, a successful fusion reactor would function as a near-unlimited source of energy.

In other words, if there’s a working demonstration of an actual fusion reactor by 2025, we could see an end to the global energy crisis within a few decades.

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Researchers have demonstrated the world’s first metasurface laser that produces “super-chiral light”: light with ultra-high angular momentum. The light from this laser can be used as a type of “optical spanner” to or for encoding information in optical communications.

“Because can carry angular , it means that this can be transferred to matter. The more angular momentum light carries, the more it can transfer. So you can think of light as an ‘optical spanner’,” Professor Andrew Forbes from the School of Physics at the University of the Witwatersrand (Wits) in Johannesburg, South Africa, who led the research. “Instead of using a physical spanner to twist things (like screwing nuts), you can now shine light on the nut and it will tighten itself.”

The new produces a new high purity “twisted light” not observed from lasers before, including the highest angular momentum reported from a laser. Simultaneously the researchers developed a nano-structured that has the largest phase gradient ever produced and allows for high power operation in a compact design. The implication is a world-first laser for producing exotic states of twisted structured light, on demand.

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Originally published by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, or AEI) in Hannover, Germany, on April 20, 2020.

The expectations of the gravitational-wave research community have been fulfilled: gravitational-wave discoveries are now part of their daily work as they have identified in the past observing run, O3, new gravitational-wave candidates about once a week. But now, the researchers have published a remarkable signal unlike any of those seen before: GW190412 is the first observation of a binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our sun. This not only has allowed more precise measurements of the system’s astrophysical properties, but it has also enabled the LIGO and Virgo scientists to verify a yet-untested prediction of Einstein’s theory of general relativity.

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