Single-pixel 'multiplex' captures elusive terahertz images

Single-pixel 'multiplex' captures elusive terahertz images: The team reports it developed a "multiplex" tunable spatial light modulator (SLM) that uses a series of filter-like "masks" to retrieve multiple samples of a terahertz (THz) scene, which are reassembled by a single-pixel detector...

Data obtained from these encoded measurements are used to computationally reconstruct the images as much as six times faster than traditional raster scan THz devices, the team reports.

First Movie Of An Entire Brain’s Neuronal Activity — The Physics arXiv Blog — Medium

First Movie Of An Entire Brain’s Neuronal Activity — The Physics arXiv Blog — Medium: ...Schrödel, Prevedel and co developed a way to ensure that the genes only fluoresce in the nucleus of each neuron. That makes active neurons much easier to tell apart...

...light sculpting. This works by bouncing the spot of laser light off a grating that stretches it out. This creates a disc of light that images an area of the brain in one go rather than a single point. In affect, it produces a cross-sectional image of brain activtiy.

The advantage is that the light disc need only be scanned in one direction to capture the whole volume of the brain. And this can be done at a rate that allows the team to film the neuronal activity of the entire brain at a rate of 80 frames per second.

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI

Ultrasonic imaging at 1,000 times times higher resolution | KurzweilAI: The researchers used a combination of subpicosecond laser pulses and unique nanostructures to produce acoustic phonons... at a frequency of 10 gigahertz (10 billion cycles per second).

By comparison, medical ultrasounds devices today typically reach a frequency of only about 20 megahertz...

“To generate 10 GHz acoustic frequencies in our plasmonic nanostructures we use a technique known as picosecond ultrasonics,” said author are Kevin O’Brien. “Sub-picosecond pulses of laser light excite plasmons which dissipate their energy as heat. The nanostructure rapidly expands and generates coherent acoustic phonons. This process transduces photons from the laser into coherent phonons.”

Continuous terahertz sources demonstrated at room temperature

Continuous terahertz sources demonstrated at room temperature: They have developed the first room-temperature, compact, continuous terahertz radiation source, and it's six times more efficient than previous systems...

The team generated terahertz radiation through nonlinear frequency mixing of two mid-infrared wavelengths at 8.8 microns and 9.8 microns from a single QCL chip. Room temperature, continuous terahertz emission with 3 microwatts is realized in a monolithic nonlinear QCL device with a tiny packaging dimension (as small as 2x5x8 mm3). This is achieved by improving the thermal conductance with epilayer-down bonding and a buried ridge waveguide, as well as by decreasing the optical loss with a buried composite grating for stable, single mode operation.

How To Build A Quantum Telescope — Medium

How To Build A Quantum Telescope — Medium: Her idea is to use the astrophysical photons to stimulate the production of an entangled pair, inside a telescope. The first of this pair then hits the detector, generating an image. But the other can be used to increase the information known about the first, thereby increasing the resolution and beating the diffraction limit.

How An Ordinary Camera Phone Can Photograph Objects Hidden Behind Other Things — The Physics arXiv Blog — Medium

How An Ordinary Camera Phone Can Photograph Objects Hidden Behind Other Things — The Physics arXiv Blog — Medium: The trick here is to treat the data from each pixel as a separate image. The task then is to look for the correlation between each of these images, just as in the single-pixel imaging techniques...

And they even produce images using reflected light (as opposed to transmitting light). To prove this, these guys recorded the light from an object that was scattered off a wall covered in white paint.

Sure enough, the resulting image revealed the object, even though it was essentially around a corner from the camera.

Magnetic charge crystals imaged in artificial spin ice

Magnetic charge crystals imaged in artificial spin ice: In the honeycomb pattern, where three magnetic poles intersect, a net charge of north or south is forced at each vertex. The magnetic "monopole charge" at each vertex influences the magnetic "charge" of the surrounding vertices. The team was able to image the crystalline structure of the magnetic charges using magnetic force microscopy...

The research team's new annealing protocol—heating the material to a high temperature where their magnetic polarity is suppressed (here, about 550 degrees Celsius)—allows the nanomagnets to flip their polarity and freely interact. As the material cools, the nanomagnets are ordered according to the interactions of their poles at the vertices...

"This work demonstrates a direction in condensed matter physics that is quite opposite to what has been done in the last sixty years or so," said Nisoli. "Instead of imagining an emergent theoretical description to model the behavior of a nature-given material and validating it indirectly, we engineer materials of desired emergent properties that can be visualized directly."

Team finds new way to use X-rays to probe properties of solid materials

Team finds new way to use X-rays to probe properties of solid materials: The energy and power density of incoming laser light can get so high that photons actually work together and nonlinear effects result from their interaction with matter. This results in materials greatly enhancing certain colors of light. In other words, if you irradiate a crystal with green light, the light that gets irradiated is actually red. This color can be precisely correlated with the structural properties of the material that is being analyzed.
Now, Alexander F�hlisch from the HZB and his team were able to observe through a series of experiments at Hamburg's short-pulse X-ray laser FLASH that these types of effects can also be achieved using soft X-rays and that this method works on solids as well. "Normally, inelastic scattering processes using soft X-rays are ineffective," explains Martin Beye, the study's primary author: "Our experiment allowed us to document how inelastic X-ray scattering can be intelligently intensified. Just like a laser, the different photons are actually working together and amplifying each other and we end up with a very high measurement signal."

Giant, Heavy and Hollow: Physicists Create Extreme Atoms

Giant, Heavy and Hollow: Physicists Create Extreme Atoms: “If you tune your X-rays properly, you can pick which shell you want to empty out first,” says Young. “Being able to control the inner-shell dynamics is very cool.” The current record for this kind of atom-hollowing was reported last November by a group at the Center for Free-electron Laser Science in Hamburg, Germany, which used the SLAC laser to strip away, from the inside out, the 36 inner electrons of a 54-electron-strong xenon atom...

In 2008, researchers led by Dunning reported that they had managed to squeeze the normally spread-out electron into a tight packet that briefly orbited the nucleus. Last year, they added radio waves that enabled that motion to be maintained indefinitely. “It only took a century, but we recreated Bohr's atom,” says Dunning proudly...

By 2002, two collaborations had been able to make as many as 50,000 atoms of antihydrogen, but the atoms quickly annihilated on the walls of their container. It took until 2010 before researchers at ALPHA showed how to trap the atoms using three magnets with a combined field sufficient to restrain antihydrogen, with its tiny magnetic moment. At that time, the antimatter was held for just 170 milliseconds, and only about one atom was trapped for every eight times the group ran the 20–30 minute experiment, says Hangst. But the team has improved its equipment to trap one atom per experiment, and hold it for about 1,000 seconds...

Imaging Breakthrough: See Atomic Bonds Before and After Molecular Reaction | Wired Science | Wired.com

Imaging Breakthrough: See Atomic Bonds Before and After Molecular Reaction | Wired Science | Wired.com: To document the graphene recipe, Fischer needed a powerful imaging device, and he turned to the atomic force microscope...

With it, the team managed to visualize not only the carbon atoms but the bonds between them, created by shared electrons. They placed a ringed carbon structure on a silver plate and heated it until the molecule rearranged. Subsequent cooling trapped the reaction products, which as it turned out, contained three unexpected products and one molecule the scientists had predicted.

A Snapshot of the Inside of an Atom - ScienceNOW

A Snapshot of the Inside of an Atom - ScienceNOW: ...the team first fired two lasers at hydrogen atoms inside a chamber, kicking off electrons at speeds and directions that depended on their underlying wave functions. A strong electric field inside the chamber guided the electrons to positions on a planar detector that depended on their initial velocities rather than on their initial positions. So the distribution of electrons striking the detector matched the wave function the electrons had at the moment they left their hydrogen nuclei behind. The apparatus displays the electron distribution on a phosphorescent screen as light and dark rings, which the team photographed using a high-resolution digital camera.

Transparent brains make neuroscience clearer

Transparent brains make neuroscience clearer: First, they remove the brain from a mouse and infuse it with a see-through gel that collects in the neurons' lipid membranes. As the gel solidifies, it takes the shape of the membranes and creates a matrix that holds the cells' proteins, DNA and RNA in place. Then the team adds a second chemical that dissolves the lipids, leaving a transparent brain made out of gel that retains the brain's proteins, DNA and RNA in their original positions.

The technique – which the researchers have named Clarity – makes it easy to see the structure of individual neurons, and preserves the fragile interconnections in near-perfect detail...

The team has successfully turned a 0.5-millimetre-thick section of human brain transparent, but working with larger chunks of human brain may be a challenge, as human neurons have a large amount of fatty protein surrounding their axons that must all be dissolved.

Close look at iron-based superconductor advances theory

Close look at iron-based superconductor advances theory: Surprisingly, however, when the material is "underdoped" with not quite enough cobalt to create superconductivity, an ordinary electric current moves easily along only one axis of the crystal—call it "lengthwise"—but encounters high resistance moving crosswise. This effect increases with the amount of cobalt doping, and may offer a clue to how superconductivity works.

Scanning tunneling microscope (STM) images of the electronic structure of the material in this underdoped state reveal an array of tiny, elongated groups of electrons in an unusual energy state, aligned with the long axis of the crystal, that act as barriers to electrons moving crosswise.

The birth of a very-high-field superconductor

The birth of a very-high-field superconductor: When cooled with liquid helium, many HTS materials, including Bi-2212, can conduct large electric currents without resistance even in the presence of huge magnetic fields. But so far scientists only have managed to turn three of these HTS materials into the long wires that are necessary to make coils. Among these materials, Bi-2212 stands out as the only HTS that can be fabricated as a round wire. This makes Bi-2212 a perfect candidate for winding cables and coils without significantly changing present magnet technology...

...they have developed a technique that prevents bubble formation almost entirely by performing the melting and re-solidification of materials under high external gas pressure. The group observed five times higher current in a long wire sample made by the new method compared to an identical sample made by the standard recipe.

New physics in iridium compounds

New physics in iridium compounds: The researchers looked at the electronic structure of Sr3CuIrO6, a compound in which the iridium atoms are surrounded by oxygen atoms in a slightly distorted octahedron.

Such a system is typically modeled by assuming that the octahedron is perfectly regular and thus the orbital degree of freedom is being quenched in certain ways. If the shape is not perfect, then the layout of the electron cloud is deformed, but previous research groups have assumed that minor irregularities made little difference and could be ignored. In this case, the structure of Sr3CuIrO6 is close to the ideal.

When the Brookhaven-led group gathered data on the actual structure, however, they found that the irregularity makes a noticeable and important change to the wave function, which thus deforms the orbitals of the active electrons, as shown in the graphic. When the spin couples to the orbitals, the effect cannot be ignored.

New metamaterials device focuses sound waves like a camera lens

New metamaterials device focuses sound waves like a camera lens: Artificial structures are created in patterns that bend the acoustic wave onto a single point, and then refocus the acoustic wave into a wider or narrower beam, depending on the direction of travel through the proposed acoustic beam aperture modifier. The acoustic beam aperture modifier is built upon gradient-index phononic crystals, in this case an array of steel pins embedded in epoxy in a particular pattern. The obstacles (steel pins) slow down the acoustic wave speed in order to bend the acoustic waves into curved rays.
According to post-doctoral scholar and the paper's lead author, Sz-Chin Steven Lin, while other types of acoustic metamaterials also could focus and defocus an acoustic beam to achieve beam aperture modification (although prior to this work no such beam modifier has been proposed), their device possesses the advantage of small size and high energy conservation.

Optimizing a novel superconducting material

Optimizing a novel superconducting material: EU researchers initiated the Hipermag project to enhance the performance of MgB2 and thus increase commercial applicability and market penetration. Researchers successfully optimised the microstructure of precursor powders, demonstrating enhanced superconducting properties of carbon-doped nanosized precursors and wires (monofilamentary tapes).

They then developed powder processing techniques leading to development of multifilamentary conductors housed in metallic sheaths. The materials provided the enhanced mechanical stability lacking until now.

Researchers also improved current-carrying capabilities, employing a variety of microscopic and spectroscopic techniques to determine the preferred orientation of MgB2 crystallites. Finally, they evaluated the stability of the superconductors in magnetic fields, explaining novel experimental results with theoretical descriptions.

YaleNews | Diamond in the rough: Half-century puzzle solved

YaleNews | Diamond in the rough: Half-century puzzle solved: A Yale-led team of mineral physicists has for the first time confirmed through high-pressure experiments the structure of cold-compressed graphite, a form of carbon that is comparable in hardness to its cousin, diamond, but only requires pressure to synthesize...
Researchers say this intermediate structure has much lower symmetry than diamond, but is as hard. In fact, “Our study shows that M-carbon is extremely incompressible and hard, rivaling the extreme properties of diamond so much that it damages diamond...”

Griffith University | News

Griffith University | News : World's first single atom photo:  Professor Kielpinski and his colleagues trapped single atomic ions of the element ytterbium and exposed them to a specific frequency of light. Under this light the atom's shadow was cast onto a detector, and a digital camera was then able to capture the image.

"By using the ultra hi-res microscope we were able to concentrate the image down to a smaller area than has been achieved before, creating a darker image which is easier to see," Professor Kielpinski said...

"If we change the frequency of the light we shine on the atom by just one part in a billion, the image can no longer be seen..."

Giant living power cables let bacteria respire

Giant living power cables let bacteria respire: IT IS the ultimate in subsea communications: bacteria living in sulphurous mud beneath the seabed respire by transforming themselves into long, insulating cables and shuttling electrons from one to another. This phenomenon has now been imaged for the first time, allowing us to see how some microbes pull off such a feat.

Some bacteria get energy by oxidising the hydrogen sulphide gas in the sediment on the ocean floor. Because there is no oxygen in the sediment to accept the electrons that are produced, bacteria such as Geobacter grow tiny filaments along which the electrons travel until they reach the oxygen in the seawater. This allows the respiration reaction to be completed.

...They found that individual bacteria, despite being only 3 to 4 micrometres long, are capable of organising themselves into giant power cables made up of several thousand bacteria. These cables can stretch to around 1 centimetre in length...

As the bacterial cells divide, the team found, they remain trapped end to end inside an ever-growing cable made up of their outer membranes. This sheath has internal fibrous ridges running along its length...

The images show the extent of the bacteria-communications network - a cubic centimetre of sediment can contain up to 1 kilometre of compacted cable...