Lifeboat Foundation

When waves damp or amplify on resonant particles in a plasma, nonresonant particles experience a recoil force that conserves the total momentum between particles and electromagnetic fields. This force is important to understand, as it can completely negate current drive and rotation drive mechanisms that are predicted on the basis of only resonant particles. Here, the existing electrostatic theory of this recoil force is extended to electromagnetic waves. While the result bears close similarity to historical fluid theories of laser–plasma interactions, it now incorporates both resonant and nonresonant particles, allowing momentum conservation to be self-consistently proven. Furthermore, the result is shown to be generally valid for kinetic plasmas, which is verified through single-particle hot-plasma simulations. The new form of the force provides physical insight into the nature of the generalized Minkowski (plasmon) momentum of geometrical optics, which is shown to correspond to the momentum gained by the field and nonresonant particles as the wave is self-consistently ramped up from vanishing amplitude.

The first measurements of a heavy oxygen isotope in Earth’s upper atmosphere suggest that isotopic concentrations could become powerful probes of atmospheric processes at otherwise hard-to-probe altitudes.

A new analysis of how the immune system responds to both older and newer investigational vaccines for respiratory syncytial virus—RSV—will help inform the ultimate translation of an immunization from the laboratory to actual clinical usage.

The research couldn’t arrive at a more crucial time. The unexpected, and dramatic, worldwide escalation of RSV cases in recent months helped demonstrate why a vaccine to prevent the infectious illness is so critically needed. Each year, RSV is responsible for 1 in 50 pediatric deaths worldwide, according to researchers at Wilhelmina Children’s Hospital in the Netherlands, where medical researchers recently completed a study on RSV.

The majority of those deaths occur among infants too young to fight the viral disease. But the infectious agent also is a killer of frail, older adults, data from the World Health Organization show, making the development of an effective vaccine a medical priority to prevent unnecessary deaths at opposite ends of the human age spectrum.

After crunching a mountain of astronomy data, Clarissa Pavao, an undergraduate at Embry-Riddle Aeronautical University’s Prescott, Arizona campus, submitted her preliminary analysis. Her mentor’s response was swift and in all-caps: “THERE’S AN ORBIT!” he wrote.

That was when Pavao, a senior space physics major, realized she was about to become a part of something big—a paper in the journal Nature that describes a rare binary star system with uncommon features.

The paper, published on Feb. 1, 2023, and co-authored with Dr. Noel D. Richardson, assistant professor of Physics and Astronomy at Embry-Riddle, describes a twin-star system that is luminous with X-rays and high in mass. Featuring a weirdly circular orbit—an oddity among binaries—the twin system seems to have formed when an exploding star or supernova fizzled out without the usual bang, similar to a dud firecracker.

If she hits just the right pitch, a singer can shatter a wine glass. The reason is resonance. While the glass may vibrate slightly in response to most acoustic tones, a pitch that resonates with the material’s own natural frequency can send its vibrations into overdrive, causing the glass to shatter.

Resonance also occurs at the much smaller scale of atoms and molecules. When particles chemically react, it’s partly due to specific conditions that resonate with particles in a way that drives them to chemically link. But atoms and molecules are constantly in motion, inhabiting a blur of vibrating and rotating states. Picking out the exact resonating state that ultimately triggers molecules to react has been nearly impossible.

MIT physicists may have cracked part of this mystery with a new study appearing in the journal Nature. The team reports that they have for the first time observed a resonance in colliding ultracold molecules.

“All things are numbers,” avowed Pythagoras. Today, 25 centuries later, algebra and mathematics are everywhere in our lives, whether we see them or not. The Cambrian-like explosion of artificial intelligence (AI) brought numbers even closer to us all, since technological evolution allows for parallel processing of a vast amounts of operations.

Progressively, operations between scalars (numbers) were parallelized into operations between vectors, and subsequently, matrices. Multiplication between matrices now trends as the most time-and energy-demanding operation of contemporary AI computational systems. A technique called “tiled matrix multiplication” (TMM) helps to speed computation by decomposing matrix operations into smaller tiles to be computed by the same system in consecutive time slots. But modern electronic AI engines, employing transistors, are approaching their intrinsic limits and can hardly compute at clock-frequencies higher than ~2 GHz.

The compelling credentials of light—ultrahigh speeds and significant energy and footprint savings—offer a solution. Recently a team of photonic researchers of the WinPhos Research group, led by Prof. Nikos Pleros from the Aristotle University of Thessaloniki, harnessed the power of light to develop a compact silicon photonic computer engine capable of computing TMMs at a record-high 50 GHz clock frequency.

Scientists have found the secret behind a property of solid materials known as ferroelectrics, showing that quasiparticles moving in wave-like patterns among vibrating atoms carry enough heat to turn the material into a thermal switch when an electrical field is applied externally.

A key finding of the study is that this control of thermal conductivity is attributable to the structure of the material rather than any random collisions among atoms. Specifically, the researchers describe quasiparticles called ferrons whose polarization changes as they “wiggle” in between vibrating atoms—and it’s that ordered wiggling and polarization, receptive to the externally applied electrical field, that dictates the material’s ability to transfer the heat at a different rate.

“We figured out that this change in position of these atoms, and the change of the nature of the vibrations, must carry heat, and therefore the external field which changes this vibration must affect the thermal conductivity,” said senior author Joseph Heremans, professor of mechanical and aerospace engineering, materials science and engineering, and physics at The Ohio State University.

With simulations that go into finer details than ever before, Brooke Polak of the University of Heidelberg and Hubert Klahr at the Max Planck Institute for Astronomy (MPIA) have modeled a key phase in the formation of planets in our solar system: the way that centimeter-size pebbles aggregate into so-called planetesimals tens to hundreds kilometers in size. The simulation reproduces the initial size distribution of planetesimals, which can be checked against observations of present-day asteroids. It also predicts the prevalence of close binary planetesimals in our solar system.

In a new study published on arXiv and accepted for publication in The Astrophysical Journal, astrophysicists Brooke Polak from the University of Heidelberg and Hubert Klahr from the Max Planck Institute for Astronomy used simulations to derive key properties of so-called planetesimals—the intermediate-size bodies from which planets formed in our solar system roughly 4.5 billion years ago.

Using an innovative method for simulating planetesimal formation, the two researchers were able to predict the initial size distribution of planetesimals in our solar system: how many are likely to have formed in the different “size brackets” between roughly 10 km and 200 km.

Think of bringing a pot of water to the boil: As the temperature reaches the boiling point, bubbles form in the water, burst and evaporate as the water boils. This continues until there is no more water changing phase from liquid to steam.

This is roughly the idea of what happened in the very early universe, right after the Big Bang, 13.7 billion years ago.

The idea comes from particle physicists Martin S. Sloth from the Center for Cosmology and Particle Physics Phenomenology at University of Southern Denmark and Florian Niedermann from the Nordic Institute for Theoretical Physics (NORDITA) in Stockholm. Niedermann is a previous postdoc in Sloth’s research group. In this new scientific article, they present an even stronger basis for their idea.