Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog – Page 3,927

A lightweight structure made of rubber and metal layers can provide an object with underwater acoustic stealth over a broad frequency range.

An acoustic “cloak” could hide an underwater object from detection by sonar devices or by echolocating marine animals. Much like camouflage clothing allows figures to fade into a background, acoustic camouflage can make an object indistinguishable from the surrounding water. Underwater acoustic cloaks have previously been demonstrated, but they typically work over a narrow range of frequencies or are too bulky to be practical. Now Hao-Wen Dong at the Beijing Institute of Technology and colleagues demonstrate a lightweight, broadband cloak made of a thin shell of layered material. The cloak achieves acoustic stealth by both blocking the reflection of sonar pings off the surface and preventing the escape of sound generated from within the cloaked object [1].

Dong and colleagues designed a 4-cm-thick structure—combining an outer rubber layer and a “metamaterial” made of porous aluminum—which covered a steel plate. Using a genetic algorithm, they optimized the metamaterial’s elastic properties to tailor the interaction with underwater sound waves. Specifically, the metamaterial converts impinging longitudinal sound waves, which can travel long distances underwater, to transverse sound waves, which cannot propagate through water. These transverse waves get trapped in the rubber layer, where they get absorbed, eliminating reflected and transmitted waves simultaneously. The researchers built and tested a prototype cloak, confirming that it behaved as predicted. In particular, it absorbed 80% of the energy of incoming sound waves while offering 100-fold attenuation of acoustic noise produced on the side of the steel plate.

Read more | >

The experimental realization of a recently proposed technique points to new possibilities for imaging molecules using x rays.

Hanbury Brown and Twiss (HBT) interferometry [1] is a versatile technique widely used in various fields of physics, such as astronomy, quantum optics, and particle physics. By measuring the correlation of photon arrival times on two detectors as a function of the photons’ spatial separation, HBT interferometry enables the determination of the size and spatial distribution of a light source. Recently, a novel x-ray imaging technique based on the HBT method was proposed to image the spatial arrangement of heavy elements in a crystal or molecule by inducing those elements to fluoresce at x-ray wavelengths [2].

Read more | >

New computer simulations show that wave-particle interactions endow thin plasmas with an effective viscosity that regulates their turbulent motions and heating.

Most of the regular matter in the Universe is plasma, an ebullient state characterized by charged particles interacting collectively with electromagnetic fields. When individual particles collide on scales much shorter than those of bulk plasma motions, the latter are described well by a 3D fluid theory: magnetohydrodynamics. That condition prevails in the interiors of stars and planets and in protoplanetary accretion disks. But many hot, low-density astrophysical plasma flows are only weakly collisional. Accounting for stellar winds, accretion around black holes, and the motions of the plasma that pervades intergalactic space requires a statistical kinetic description of the particle positions and velocities in a 6D space. Numerical simulations by Lev Arzamasskiy of the Institute of Advanced Study in Princeton, New Jersey, and his colleagues [1] shed new light on magnetized kinetic turbulence in such plasmas.

Read more | >

Over the past 100 million years, mammals have adapted to nearly every environment on Earth. Scientists with the Zoonomia Project have been cataloging the diversity in mammalian genomes by comparing DNA sequences from 240 species that exist today, from the aardvark and the African savanna elephant to the yellow-spotted rock hyrax and the zebu.

This week, in several papers in a special issue of Science, the Zoonomia team has demonstrated how can not only shed light on how certain species achieve extraordinary feats, but also help scientists better understand the parts of our genome that are functional and how they might influence health and disease.

In the new studies, the researchers identified regions of the genomes, sometimes just single letters of DNA, that are most conserved, or unchanged, across mammalian species and millions of years of evolution—regions that are likely biologically important. They also found part of the genetic basis for uncommon mammalian traits such as the ability to hibernate or sniff out faint scents from miles away. And they pinpointed species that may be particularly susceptible to extinction, as well as genetic variants that are more likely to play causal roles in rare and common human diseases.

Read more | >

An international research team led by investigators at Virginia Commonwealth University has identified for the first time markers that may indicate early in life if a person has susceptibility to schizophrenia.

The ability to predict the risk of developing later in life may allow early detection and intervention, which the researchers hope can reduce the impact of the disease on individuals, families and communities. Their results have been published in Molecular Psychiatry.

Schizophrenia is a serious psychiatric disorder that is most often detected in young adulthood. It affects as much as 1% of the and can cause debilitating effects such as a sense of losing touch with reality. People with the disorder are up to three times more likely to die early and often face discrimination, social isolation and debilitating physical illness, according to the World Health Organization.

Read more | >

Emerging AI applications, like chatbots that generate natural human language, demand denser, more powerful computer chips. But semiconductor chips are traditionally made with bulk materials, which are boxy 3D structures, so stacking multiple layers of transistors to create denser integrations is very difficult.

However, semiconductor transistors made from ultrathin 2D materials, each only about three atoms in thickness, could be stacked up to create more powerful chips. To this end, MIT researchers have now demonstrated a that can effectively and efficiently “grow” layers of 2D transition metal dichalcogenide (TMD) materials directly on top of a fully fabricated silicon chip to enable denser integrations.

Growing 2D materials directly onto a silicon CMOS wafer has posed a major challenge because the process usually requires temperatures of about 600 degrees Celsius, while silicon transistors and circuits could break down when heated above 400 degrees. Now, the interdisciplinary team of MIT researchers has developed a low-temperature growth process that does not damage the chip. The technology allows 2D semiconductor transistors to be directly integrated on top of standard silicon circuits.

Read more | >

SAN FRANCISCO –New Hampshire startup Light Steering Technologies won a $1.25 million U.S. Air Force contract for angular pointing technology with small satellite applications.

Through the contract with AFWERX, the Air Force organization focused on innovation, LST aims to advance the Technology Readiness Level, or technological maturity, of its Multi-Axis Scanner. LST’s Multi-Axis Scanner is a patented magnetic joint for gimbal-like capability.

“What’s compelling about the technology is we are minimizing the moving mass,” Aaron Castillo, LST senior vice president of business development and program management, told SpaceNews. “This is achieved by actuating a mirror instead of the entire satellite bus or using a traditional gimbal mechanism.”

Read more | >

For one, classical physics can predict, with simple mathematics, how an object will move and where it will be at any given point in time and space. How objects interact with each other and their environments follow laws we first encounter in high school science textbooks.

What happens in minuscule realms isn’t so easily explained. At the level of atoms and their parts, measuring position and momentum simultaneously yields only probability. Knowing a particle’s exact state is a zero-sum game in which classical notions of determinism don’t apply: the more certain we are about its momentum, the less certain we are about where it will be.

We’re not exactly sure what it will be, either. That particle could be both an electron and a wave of energy, existing in multiple states at once. When we observe it, we force a quantum choice, and the particle collapses from its state of superposition into one of its possible forms.

Read more | >