Researchers build optical invisibility cloak for a diffusive medium

Researchers build optical invisibility cloak for a diffusive medium: ...The tank was filled with a white, turbid liquid. Objects inside cast a visible shadow onto the tank wall. Simple metal cylinders or spheres of a few centimeters in diameter were used as test objects... To pass the light around the object, the researchers applied a thin shell made of the transparent silicon material PDMS, to which a certain concentration of light-scattering melamine microparticles was added. The silicon/melamine shell caused a quicker diffusion than in the environment and, thus, passed the light around the objects...

"Ideal optical invisibility cloaks in air have a drawback... They violate Albert Einstein's theory of relativity that prescribes an upper limit for the speed of light.  In diffuse media, in which light is scattered several times, however, the effective speed of light is reduced. Here, ideal invisibility cloaks can be realized."

Watch a singularity form in a stretchy soap film - physics-math - 28 May 2014 - New Scientist

Watch a singularity form in a stretchy soap film - physics-math - 28 May 2014 - New Scientist

Fire ants writhe to make unsinkable rafts - life - 26 November 2013 - New Scientist

Fire ants writhe to make unsinkable rafts - life - 26 November 2013 - New Scientist: A raft of live fire ants, on the other hand, resists and dissipates external forces equally well on all scales. The ants can act as tiny, resistive springs by flexing and extending their legs, and they break and reform connections with their neighbours to create a flow around external forces, like being prodded with sticks. Importantly, rafts of live ants are significantly more elastic than those made of flash-frozen dead ants.

IBM unveils concept for a future brain-inspired 3D computer | KurzweilAI

IBM unveils concept for a future brain-inspired 3D computer | KurzweilAI: IBM has unveiled a prototype of a new brain-inspired computer powered by what it calls “electronic blood,” BBC News reports.

The firm says it is learning from nature by building computers fueled and cooled by a liquid, like our minds...

Its new “redox flow” system pumps an electrolyte “blood” through a computer, carrying power in and taking heat out.

Bizarre Liquid More Stable Than Solid Crystal | LiveScience

Bizarre Liquid More Stable Than Solid Crystal | LiveScience: "When we make the bonds more flexible, the liquid phase remains stable even at extremely low temperatures," Smallenburg said. "The particles will simply never order into a crystal, unless they are compressed to high densities." �

What does mercury being liquid at room temperature have to do with Einstein’s theory of relativity? | The Curious Wavefunction, Scientific American Blog Network

What does mercury being liquid at room temperature have to do with Einstein’s theory of relativity? | The Curious Wavefunction, Scientific American Blog Network:  From Niels Bohr’s theory of atomic structure we know that the velocity of an electron is proportional to the atomic number of an element. For light elements like hydrogen (atomic number 1) the velocity is insignificant compared to the speed of light so relativity can be essentially ignored. But for the 1s electron of mercury (atomic number 80) this effect becomes significant; the electron approaches about 58% of the speed of light, and its mass increases to 1.23 times its rest mass. Relativity has kicked in. Since the radius of an electron orbit in the Bohr theory (orbital to be precise) goes inversely as the mass, this mass increase results in a 23% decrease in the orbital radius. This shrinkage makes a world of difference since it results in stronger attraction between the nucleus and the electrons, and this effect translates to the outermost 6s orbital as well as to other orbitals. The effect is compounded by the more diffuse d and f orbitals insufficiently shielding the s electrons. Combined with the filled nature of the 6s orbital, the relativistic shrinkage makes mercury very reluctant indeed to share its outermost electrons and form strong bonds with other mercury atoms.

The bonding between mercury atoms in small clusters thus mainly results from weak Van der Waals forces which arise from local charge fluctuations in neighboring atoms rather than the sharing of electrons.

'Liquid-liquid' phase transition: Researchers identify transformation in low-temperature water

'Liquid-liquid' phase transition: Researchers identify transformation in low-temperature water; Through a simulation performed in "supercooled" water, a research team led by chemist Feng "Seymour" Wang, confirmed a "liquid-liquid" phase transition at 207 Kelvins, or 87 degrees below zero on the Fahrenheit scale.
The properties of supercooled water are important for understanding basic processes during cryoprotection, which is the preservation of tissue or cells by liquid nitrogen so they can be thawed without damaged...

New phase of water could dominate the interiors of Uranus and Neptune

New phase of water could dominate the interiors of Uranus and Neptune: One lesser known phase of water is the superionic phase, which is considered an "ice" but exists somewhere between a solid and a liquid: while the oxygen atoms occupy fixed lattice positions as in a solid, the hydrogen atoms migrate through the lattice as in a fluid. Until now, scientists have thought that there was only one phase of superionic ice, but scientists in a new study have discovered a second phase that is more stable than the original.

...the simulations show that a phase transition between the bcc and fcc phases may exist at pressures of 1.0 ± 0.5 Mbar.

...Uranus and Neptune we've just done brief flybys with Voyager 2. What we do know is that they have bizarre non-axisymmetric non-dipolar magnetic fields, totally unlike any other planet in our solar system.

Solid or Liquid? Physicists Redefine States of Matter

Solid or Liquid? Physicists Redefine States of Matter: ...the main difference between liquids and solids is the way they respond to shear, or twisting forces. Liquids barely resist shear and can easily be sloshed, whereas solids — regardless of whether they are crystals, quasicrystals or glass — resist attempts to change their shape.

The liquid-solid phase transition, Radin and Aristoff reason, should therefore be marked by the “shear response” of a material jumping from zero to a positive value...

Shrinking Blob Computes Travelling Salesman Solutions

Shrinking Blob Computes Travelling Salesman Solutions:  In simplified terms, the blob clings to the dots as it shrinks, linking them with a minimal surface, rather like a soap bubble surface. “As the blob shrinks it morphologically adapts to the configuration of the cities,” they say...

The magic ingredient in all this is the special goo. It consists of many particles that each move according to a set of simple rules, like autonomous agents. These sit in a sea of “chemoattractant”, a virtual scent that the particles are attracted to.  At each stage in the calculation, each particle senses the chemoattractant around it and then moves towards the region of highest concentration. As it moves, it leaves behind its own trace of the chemoattractant for other particles to follow.

First fluid knots created in the lab

First fluid knots created in the lab: To investigate, Dustin Kleckner and William Irvine of the University of Chicago, Illinois 3D-printed strips of plastic shaped into a trefoil knot and a Hopf link. Crucially, the strips had a cross section shaped like a wing, or hydrofoil (see picture).

Next, the researchers dragged the knots through water filled with microscopic bubbles. Just as a wing passing through air creates a trailing vortex, the acceleration of the hydrofoils created a knot-shaped vortex that sucked in the bubbles. The result was a knot-shaped flow of moving bubbles – the first fluid knot created in a lab – which the team imaged with lasers.

First Toy Multiverse Created in a Laboratory, Say Physicists

First Toy Multiverse Created in a Laboratory, Say Physicists: Cobalt is ferromagnetic so the nanoparticles tend to become aligned in a magnetic field. In fact, if the density of nanoparticles is high enough, the field causes them to line up in columns. When this happens, the nanocolumns form a metamaterial which is mathematically equivalent to a 2+1 Minkowski spacetime...


The secret here is to keep the density of nanoparticles just below the threshold required to form nanocolums. That’s just over 8 per cent of the fluid by volume in this case. When that happens, natural variations in the density cause nanocolumns to form in small regions of the liquid. In effect, tiny universes are leaping in and out of existence. Smolyaninov and co can even “see” these universes by their effect on polarised light passing through the fluid.

That’s a fascinating result that demonstrates the potential of self-organisation to create metamaterials.

Physicists Find a Backdoor Way to Do Experiments on Exotic Gravitational Physics

Physicists Find a Backdoor Way to Do Experiments on Exotic Gravitational Physics: But what about running the dualities in the other direction, using laboratory measurements of extreme materials to probe exotic gravitational physics?...
The experiments in question entail smashing gold or lead nuclei together to create plasmas of quarks and gluons...
The plasmas must actually be liquid...

They equated the viscosity of a fluid to gravitational waves caroming off a black hole in higher-dimensional space—which, even for a physicist, is not an analogy that springs to mind...

The answer: 1/4π, in the appropriate units. The viscosity measured by RHIC comes close. Water, some 400 times more viscous, is molasses in comparison.

Surprisingly, the minimum value is the same for all fluids, whatever they are made of. Through the logic of duality, this universality has a simple explanation: Viscosity is equivalent to a gravitational phenomenon, and according to Einstein’s general theory of relativity, gravitation is blind to compositional details.

Topology: The Secret Ingredient In The Latest Theory of Everything

Topology: The Secret Ingredient In The Latest Theory of Everything: Today, Wen combines topology, symmetry and quantum mechanics in a new theory that predicts the existence of new states of matter, unifies various puzzling phenomena in solid state physics and allows the creation artificial vacuums populated with artificial photons and electrons...

Xiao-Gang Wen's approach is to explore the properties of matter when the topological links between particles become much more general and complex. He generalises these links, thinking of them as strings that can connect many  particles together. In fact, he considers the way many strings can form net-like structures that have their own emergent properties...
That makes string nets a kind of "quantum ether" through which electromagnetic waves travel. That's a big claim.

Acoustic tweezers capture tiny creatures with ultrasound (w/ Video)

Acoustic tweezers capture tiny creatures with ultrasound (w/ Video): Acoustic tweezers use ultrasound, the same noninvasive technology doctors use to capture images of the fetus in the womb. The device is based on piezoelectric material that moves when under an electrical current. The vibrations pass through transducers attached to the piezoelectric substrate, where they are converted into standing surface acoustic waves (SAWs). The SAWs create pressure fields in the liquid medium that hold the specimen...
"We believe the device can be easily manufactured at a cost far lower than say, optical tweezers, which use lasers to manipulate single particles," said Tony Jun Huang, associate professor of bioengineering, whose group pioneered acoustic tweezers. "Optical tweezers require power densities 10,000,000 times greater than our acoustic tweezers, and the lasers can heat up and damage the cells, unlike ultrasound."

Liquid-Filled Robot Finger More Sensitive to Touch Than a Human's

Liquid-Filled Robot Finger More Sensitive to Touch Than a Human's: A flexible, spongy skin complete with ridges (like a fingerprint) is stretched over a liquid filling. As it slides over a surface, the skin vibrates in ways that are distinctly tied to the texture of the material it is touching. A hydrophone inside the core of the finger picks up these vibrations and uses them to distinguish between materials...

The researchers recreated this way of discerning between exploratory movements via an algorithm that allows the robot to zero in on the best exploratory movements for appraising any material set in front of it at random. The result: when presented with 117 materials gathered from fabric, stationary, and hardware stores, the robot correctly identified them 95 percent of the time using no sensory input but touch.

Video: Micro-Robots Made of Bubbles That Are Powered by Lasers | Popular Science

Video: Micro-Robots Made of Bubbles That Are Powered by Lasers | Popular Science: Using nothing more than a fine-tipped syringe filled with air and saline solution, Ohta and his colleagues in the U.H. Department of Electrical Engineering have created a system that uses a 400 mW infrared laser to propel bubbles around their environment. The laser is shone straight through the bubble, where it heats the far side...
The velocity of the bubbles correlates to the intensity of the laser, so speed can be manipulated by dialing the laser up or down...
Unlike other micromechanical machines, which are often controlled by magnetic fields, they are also independently steerable--each bubble simply requires its own laser source. Where a swarm of microbots controlled via magnetism would tend to clump together as they respond to a common magnetic field, the laser-controlled bubble-bots can be steered separately with an array of infrared lasers.

Liquid could power and cool mobile supercomputers

Liquid could power and cool mobile supercomputers: Michel and his team's idea is to stack hundreds of silicon wafers on top of each other to create three-dimensional processors. Between each layer is a pair of fluidic networks. One of these carries in charged fluid to power the chip, while the second carries away the same fluid after it has picked up heat from the active transistors - effectively creating a microscopic flow battery...
"The use of liquid to cool 3D chips is not new," says Bob Patti, chief technology officer of Tezzaron. "However, using the liquid as a power source as well as for cooling is a concept I haven't seen before."

New Scientist TV: Spiny ferrofluid performs magnetic ballet

New Scientist TV: Spiny ferrofluid performs magnetic ballet: In this video, ferrofluid spikes take to the floor and perform a magnetised dance. Created by engineer Tatyana Arefyeva at the Ivanovo State Power University in Russia, the spiny ballet exploits the magnetic fields of a ferrofluid. Using a computer program to manipulate these fields, Arefyeva made the substance change shape. The particles align themselves along field lines moving with the magnetic force. When the field is turned off, they return to a random alignment.

Look ma, no hands: Engineers invent a magnetic fluid pump with no moving parts

Look ma, no hands: Engineers invent a magnetic fluid pump with no moving parts: The ferrohydrodynamic pump method works when electrodes wound around a pipe force magnetic nanoparticles within the ferrofluids to rotate at varying speeds.  Those particles closest to the electrodes spin faster, and it is this spatial variation in rotation speed that propels the ferrofluid forward. "We don't rely on any other material; no magnets, nothing moving but the ferrofluid that we're pumping," Koser says.