A new path to understanding second sound in …

A new path to understanding second sound in Bose-Einstein condensates

There are two sound velocities in a Bose-Einstein condensate. In addition to the normal sound propagation there is second sound, which is a quantum phenomenon. Scientists in Ludwig Mathey’s group from the University of Hamburg have put forth a new theory for this phenomenon.

When you jump into a lake and hold your head under water, everything sounds different. Apart from the different physiological response of our ears in air and water, this derives from the different sound propagation in water compared to air. Sound travels faster in water, checking in at 1493 m/s, on a comfortable summer day of 25°C. Other liquids have their own sound velocity, like alcohol with 1144 m/s, and helium, if you go to a chilling -269°C for its liquefied state, with 180 m/s.

These liquids are referred to as classical liquids, examples for one of the primary states of matter. But if we cool down that helium a few degrees more, something dramatic happens, it turns into a quantum liquid. This macroscopic display of quantum mechanics is a superfluid, a liquid that flows without friction.

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Building next gen smart materials with the pow…

Building next gen smart materials with the power of sound

Metal-organic frameworks, or MOFs, are incredibly versatile and super porous nanomaterials that can be used to store, separate, release or protect almost anything.

Predicted to be the defining material of the 21st century, MOFs are ideal for sensing and trapping substances at minute concentrations, to purify water or air, and can also hold large amounts of energy, for making better batteries and energy storage devices.

Scientists have designed more than 88,000 precisely-customised MOFs – with applications ranging from agriculture to pharmaceuticals – but the traditional process for creating them is environmentally unsustainable and can take several hours or even days.

Now researchers from RMIT University in Melbourne, Australia, have demonstrated a clean, green technique that can produce a customised MOF in minutes.

Dr Heba Ahmed, lead author of the study published in Nature Communications, said the efficient and scaleable method harnessed the precision power of high-frequency sound waves.

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How to pop open soft nanoparticles using sou…

How to pop open soft nanoparticles using sound waves

Ultrasound has long been an important tool for medical imaging. Recently, medical researchers have demonstrated that focused ultrasound waves can also improve the delivery of therapeutic agents such as drugs and genetic material. The waves form bubbles that make cell membranes—as well as synthetic membranes enclosing drug-carrying vesicles—more permeable. However, the bubble-membrane interaction is not well understood.

Soft lipid shells, insoluble in water, are a key component of the barrier that surrounds cells. They are also used as drug nanocarriers: nanometer size particles of fat or lipid molecules that carry the drug to be delivered locally at the diseased organ or location, and which can be injected inside the body.

The lipid shell can be “popped” by soundwaves, which can be focused to a spot around the size of a grain of rice, resulting in a highly localized opening of barriers potentially overcoming major challenges in drug delivery.

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Academics show how to create a spotlight of …

Academics show how to create a spotlight of sound with LEGO-like bricks

Informatics experts create low-cost directional beams of sound

Academics have created devices capable of manipulating sound in the same way as light – creating exciting new opportunities in entertainment and public communication.

Researchers at the universities of Sussex and Bristol have unveiled how the practical laws used to design optical systems can also be applied to sound through acoustic metamaterials at the ACM CHI Conference on Human Factors in Computing Systems.

The researchers have demonstrated the first dynamic metamaterial device with the zoom objective of a varifocal for sound. The project team have also built a collimator, capable of transmitting sound as a directional beam from a standard speaker.

The breakthrough has the potential to revolutionise the entertainment industry as well as many aspects of communication in public life by creating directional speakers that can reach out to an individual in a crowd.

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Stickier than expected: Hydrogen binds to gr…

Stickier than expected: Hydrogen binds to graphene in 10 femtoseconds

Bound for only ten quadrillionths of a second

Graphene is celebrated as an extraordinary material. It consists of pure carbon, only a single atomic layer thick. Nevertheless, it is extremely stable, strong, and even conductive. For electronics, however, graphene still has crucial disadvantages. It cannot be used as a semiconductor, since it has no bandgap. By sticking hydrogen atoms to graphene such a bandgap can be formed. Now researchers from Göttingen and Pasadena (USA) have produced an “atomic scale movie” showing how hydrogen atoms chemically bind to graphene in one of the fastest reactions ever studied.

The international research team bombarded graphene with hydrogen atoms. “The hydrogen atom behaved quite differently than we expected,” says Alec Wodtke, head of the Department of Dynamics at Surfaces at the Max Planck Institute (MPI) for Biophysical Chemistry and professor at the Institute of Physical Chemistry at the University of Göttingen. “Instead of immediately flying away, the hydrogen atoms ‘stick’ briefly to the carbon atoms and then bounce off the surface. They form a transient chemical bond,” Wodtke reports. And something else surprised the scientists: The hydrogen atoms have a lot of energy before they hit the graphene, but not much left when they fly away. Hydrogen atoms lose most of their energy on collision, but where does it go?

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New inspection process freezes parts in ice

New inspection process freezes parts in ice

“How on Earth did they make that?” asks Francesco Simonetti, commenting on an ice sculpture of a swan.

Simonetti isn’t admiring the artistry of shaping a block of ice into a bird. He’s admiring the swan’s crystal-clear transparency.

Simonetti, an aerospace engineering professor at the University of Cincinnati, is an expert in sound waves, but lately he’s been an apprentice in ice. And when it comes to sound waves, the clearer the ice, the better.

Simonetti recently published a novel approach that uses ultrasound to inspect additive-manufactured parts: He dips the part in water and freezes it inside a cylinder of ice. The ice acts as a coupling medium, letting ultrasonic waves enter and reflect against the part’s potential defects.

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