Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: materials – Page 240

TEPIC, Mexico (Thomson Reuters Foundation) — Tequila, avocado and corn are proving their worth beyond Mexican fiesta staples as key components for a fast-growing bioplastics market, with companies transforming waste from processing food crops into products such as bags, plates and even car parts.

Bioplastics make up less than 5 percent of the millions of tonnes of plastic produced each year around the world.

But as governments and consumers fret about the damage plastic is doing to the world’s oceans, scientists are experimenting by converting materials from cactus to shrimp shells and human waste into alternative greener plastics.

Read more | >

Supersolids, solid materials with superfluid properties (i.e., in which a substance can flow with zero viscosity), have recently become the focus of numerous physics studies. Supersolids are paradoxical phases of matter in which two distinct and somewhat antithetical orders coexist, resulting in a material being both crystal and superfluid.

First predicted at the end of the 1960s, supersolidity has gradually become the focus of a growing number of research studies, sparking debate across different scientific fields. Several years ago, for instance, a team of researchers published controversial results that identified this phase in solid helium, which were later disclaimed by the authors themselves.

A key issue with this study was that it did not account for the complexity of helium and the unreliable observations that it can sometimes produce. In addition, in atoms, interactions are typically very strong and steady, which makes it harder for this phase to occur.

Read more | >

Two separate teams of scientists have devised novel hydrodynamic “invisibility cloaks”—instead of shielding objects from light, the cloaks would shield them from fluid flows. The scientists described their work in two new papers in Physical Review Letters. These kinds of cloaking structures could one day help reduce drag on ships or submarines, or protect ships at a port or wharf from potential damage from strong waves.

Most so-called “invisibility cloaks” created thus far work in the electromagnetic regime and rely on metamaterials. A “metamaterial” is any material whose microscopic structure can bend light in ways light doesn’t normally bend—a property called “the index of refraction.” Natural materials have a positive index of refraction; certain manmade metamaterials—first synthesized in the lab in 2000—have a negative index of refraction, meaning they interact with light in such a way as to bend light around even very sharp angles.

Read more | >

At human scale, controlling temperature is a straightforward concept. Turtles sun themselves to keep warm. To cool a pie fresh from the oven, place it on a room-temperature countertop.

At the nanoscale—at distances less than 1/100th the width of the thinnest human hair—controlling temperature is much more difficult. Nanoscale distances are so small that objects easily become thermally coupled: If one object heats up to a certain temperature, so does its neighbor.

When scientists use a as that , there is an additional challenge: Thanks to heat diffusion, materials in the beam path heat up to approximately the same temperature, making it difficult to manipulate the thermal profiles of objects within the beam. Scientists have never been able to use light alone to actively shape and control thermal landscapes at the nanoscale.

Read more | >

It’s a problem that plagues even the priciest of lenses, manufactured to the most exacting specifications: the center of the frame might be razor-sharp, but the corners and edges always look a little soft. It’s a problem that’s existed for thousands of years with optical devices, and one that was assumed to be unsolvable until a Mexican physicist developed a mind-melting formula that could revolutionize how lenses are manufactured.

On paper, a curved glass lens should be able to redirect all the rays of light passing through it onto a single target known as its focal point. But in the real world, it just doesn’t work that way. Differences in refraction across the lens, as well as imperfections in its shape and materials, all contribute to some of those light rays, especially those entering the lens near its outer edges, missing the target. It’s a phenomenon known as spherical aberration, and it’s a problem that even Isaac Newton and Greek mathematician Diocles couldn’t crack.

Read more | >

Some call it a SASER and others call it a PHASER.

How do you whisper to someone across the room? With lasers, of course. MIT has developed a system using lasers to transmit audio signals directly to the ear, and no one else in the area can hear them. As a nice bonus, the laser won’t burn your skin or eyes should you turn your head at the wrong moment.

The laser system leverages what is known as the photoacoustic effect. That simply means that the absorption of light waves by a material produces sound waves. In this case, the light is absorbed by water molecules in the air, but the researchers learned to very carefully tune the laser to control where the sound appears. It’s essentially a narrow cone of sound.

Making sound with a laser is one thing, but creating specific tones or transmitting a message is much harder. The team evaluated two methods for doing this. First, there’s the laser sweeping technique, which involves altering the wavelength of light to create different sounds. The traditional photoacoustic method uses varying power to encode a message.

Continue reading “MIT Creates Lasers That Whisper in Your Ear” | >