Aurelia Butler

In nature, many things have evolved that differ in size, color and, above all, in shape. While the color or size of an object can be easily described, the description of a shape is more complicated. In a study now published in Nature Communications, Jacqueline Nowak of the Max Planck Institute of Molecular Plant Physiology and her colleagues have outlined a new and improved way to describe shapes based on a network representation that can also be used to reassemble and compare shapes.
Jacqueline Nowak designed a novel approach that relies on a network-based shape representation, named visibility graph, along with a tool for analyzing shapes, termed GraVis. The visibility graph represents the shape of an object that is defined by its surrounding contour and the mathematical structure behind GraVis is specified by a set of nodes equidistantly placed around the contour. The nodes are then connected with each other by edges, that do not cross or align with the shape boundary.As a result, testing the connection between all pairs of nodes specifies the visibility graph for the analyzed shape.
In this study, Jacqueline Nowak used the visibility graphs and the GraVis tool to compare different shapes. To test the power of the new approach, visibility graphs of simple triangular, rectangular and circular shapes, but also complex shapes of sand grains, fish shapes and leaf shapes were compared with each other.
By using different machine learning approaches, they demonstrated that the approach can be used to distinguish shapes according to their complexity. Furthermore, visibility graphs enable to distinguish the complexity of shapes as it was shown for epidermal pavement cells in plants, which have a similar shape to pieces of jigsaw puzzle. For these cells, distinct shape parameters like lobe length, neck width or cell area can be accurately quantified with GraVis. “The quantification of the lobe number of epidermal cells with GraVis outperforms existing tools, showing that it is a powerful tool to address particular questions relevant to shape analysis,” says Zoran Nikoloski, GraVis project leader, head of the research group “Systems biology and Mathematical Modelling” at the Max Planck Institute of Molecular Plant Physiology and Professor of Bioinformatics at University of Potsdam.
In future, the scientists want to apply visibility graphs of epidermal cells and entire leaves to gain biological insights of key cellular processes that impact shape. In addition, shape features of different plant cells quantified by GraVis can facilitate genetic screens to determine the genetic basis of morphogenesis. Finally, the application of GraVis will help to gain deeper understanding of the interrelation between cells and organ shapes in nature.

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With Japan’s society rapidly aging, there has been a sharp increase in patients who experience motor dysfunctions. Rehabilitation is key to overcoming such ailments.
A researcher from Tohoku University has developed a new virtual reality (VR) based method that can benefit rehabilitation and sports training by increasing bodily awareness and?improving motor control.
His research was published in the Journal Scientific Report.
Not only can we see and touch our body, but we can sense it too. Our body is constantly firing off information to our brains that tell us where our limbs are in real-time. This process makes us aware of our body and gives us ownership over it. Meanwhile, our ability to control the movement and actions of our body parts voluntarily affords us agency over our body.
Ownership and agency are highly integrated and are related to our motor control. However, separating our sense of body ownership from our sense of agency has long evaded researchers, making it difficult to ascertain whether both ownership and agency truly affect motor control.
Professor Kazumichi Matsumiya from the Graduate School of Information Sciences at Tohoku University could isolate these two senses by using VR. Participants viewed a computer-generated hand, and Matsumiya independently measured their sense of ownership and agency over the hand.
“I found that motor control is improved when participants experienced a sense of agency over the artificial body, regardless of their sense of body ownership,” said Matsumiya. “Our findings suggest that artificial manipulation of agency will enhance the effectiveness of rehabilitation and aid sports training techniques to improve overall motor control.”

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Researchers say they have been able to greatly improve the readout of data from digital memories — thanks to a phenomenon known as ‘quantum entanglement’.
The research team, which included researchers from the Italian Institute of Metrological Research (INRIM) and the University of York, say the findings could have major applications for digital storage devices, including optical memories such as CD or BluRay disks.
This is the first experimental demonstration that quantum sources of light can enhance the readout of information from digital memories, an advance that could potentially lead to faster access of data in large databases and to construct memories with higher capacities in our next-generation computers.
In an optical memory, bits are read by shining a laser beam over the reflecting surface of the disk. In the memory, each microscopic cell has one of two possible levels of reflectivity, representing the values “zero” and “one” of a bit.
As a result, the laser beam reflected from a cell may be more or less intense depending on the value of the bit. The intensity of the beam is then registered by a detector and finally translated into an electrical signal.
However, when the intensity of the laser beam becomes too low, for example as a result of an increased speed of the disk, energy fluctuations prevent the correct retrieval of the bits, introducing too many errors.
The study showed how to fix this problem by resorting to more sophisticated light sources, where the use of quantum entanglement completely removes the unwanted fluctuations.
The researchers say the consequences of the study go far beyond applications to digital memories. In fact, the same principle can be used in spectroscopy and the measurement of biological samples, chemical compounds and other materials.
The scheme also paves the way for non-invasive, ultra-sensitive measurements by greatly reducing the optical power without reducing the amount of information recovered from the systems.
Another promising perspective explored by the researchers is to extend the method to the recognition of complex patterns in conjunction with modern machine-learning algorithms, with potential implications for bio-imaging.
Professor Stefano Pirandola, from the Department of Computer Science at the University of York, said: “This experiment finally shows how we can harness quantum entanglement to better read information from memory devices and other physical systems.”

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Scientists at the University of Bonn have built hair-thin optical fibre filters in a very simple way. They are not only extremely compact and stable, but also colour-tunable. This means they can be used in quantum technology and as sensors for temperature or for detecting atmospheric gases. The results have been published in the journal Optics Express.
Optical fibers not much thicker than a human hair today not only constitute the backbone of our world-wide information exchange. They are also the basis for building extremely compact and robust sensors with very high sensitivity for temperature, chemical analysis and much more.
Optical resonators or filters are important components cutting out very narrow spectral lines from white light sources. In the simplest case such filters are built from two opposing mirrors tossing light back and forth as precisely as the pendulum of a clock work. The color of the filtered light is set by the mirror separation.
Suitable mirrors with high quality have been integrated with the end of such hairlike fibers for some time. Researchers of the University of Bonn have succeeded to build in a simple way such hairlike optical fiber resonators. They are not only extremely compact and stable but also allow to tune their color: they have glued the fiber ends carrying the mirrors into a common ferrule which can be stretched by means of a piezo crystal and hence control the mirror separation.
“The miniaturised optical filter makes a further contribution to making photonics and quantum technologies the decisive technology of the 21st century,” says Prof. Dr. Dieter Meschede from the Institute of Applied Physics at University of Bonn. The scientist is a member of “Matter and light for quantum computing” (ML4Q) Cluster of Excellence of the Universities of Bonn and Cologne and RWTH Aachen University and is also a member of the Transdisciplinary Research Area “Building Blocks of Matter and Fundamental Interactions” at the University of Bonn.
Miniaturized highly stable optical precision filters are promising multiple applications: they can store light energy within such a small volume such that already single photons can be efficiently stored and manipulated. Their high sensitivity suggests to build extremely compact and selective sensors, e.g. for detecting atmospheric gases. Using even more stable materials for the ferrule tiny optical clock works with extremely high frequency stability may be built.

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Robots are widely used to build cars, paint airplanes and sew clothing in factories, but the assembly of microscopic components, such as those for biomedical applications, has not yet been automated. Lasers could be the solution. Now, researchers reporting in ACS Applied Materials & Interfaces have used lasers to create miniature robots from bubbles that lift, drop and manipulate small pieces into interconnected structures.
As manufacturing has miniaturized, objects are now being constructed that are only a few hundred micrometers long, or about the thickness of a sheet of paper. But it is hard to position such small pieces by hand. In previous studies, scientists created microscopic bubbles using light or sound to assemble 2D items. Also, in a recent experiment, microbubbles produced by lasers, focused and powerful beams of light, could rotate shapes in 3D space. Although these bubble microrobots could manipulate 2D and 3D objects, they could not connect independent components and then move them as a singular entity. So, Niandong Jiao, Lianquing Liu and colleagues wanted to build on their previous work with lasers to develop bubble microbots that can form inseparable shapes and control their movement.
The researchers created microbubbles in water by focusing a laser underneath a small part made of resin. The bubble’s size was controlled by rapidly switching the laser on and off, with a higher amount of time in the “on position” resulting in larger bubbles. Then, the team made a mobile bubble robot by shifting the laser’s location. Once the laser turned off, the bubbles dissolved slowly, dropping the resin in place. The team then combined multiple bubbles with different functions to produce microrobots that could lift and drop parts, move single pieces to designated positions, act as a rotational axis or push assembled objects. Unbreakable connections were made with various joints, producing three- and four-pronged gears, a snake-shaped chain and a miniature 3D vehicle. The bubble microrobots have implications for the future of manufacturing, including biological tissue engineering, the researchers say.

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A team of researchers from the Faculty of Pure and Applied Sciences at the University of Tsukuba filmed the ultrafast motion of electrons with sub-nanoscale spatial resolution. This work provides a powerful tool for studying the operation of semiconductor devices, which can lead to more efficient electronic devices.
The ability to construct ever smaller and faster smartphones and computer chips depends on the ability of semiconductor manufacturers to understand how the electrons that carry information are affected by defects. However, these motions occur on the scale of trillionths of a second, and they can only be seen with a microscope that can image individual atoms. It may seem like an impossible task, but this is exactly what a team of scientists at the University of Tsukuba was able to accomplish.
The experimental system consisted of Buckminsterfullerene carbon molecules — which bear an uncanny resemblance to stitched soccer balls — arranged in a multilayer structure on a gold substrate. First, a scanning tunneling microscope was set up to capture the movies. To observe the motion of electrons, an infrared electromagnetic pump pulse was applied to inject electrons into the sample. Then, after a set time delay, a single ultrafast terahertz pulse was used to probe the location of the elections. Increasing the time delay allowed the next “frame” of the movie to be captured. This novel combination of scanning tunneling microscopy and ultrafast pulses allowed the team to achieve sub-nanoscale spatial resolution and near picosecond time resolution for the first time. “Using our method, we were able to clearly see the effects of imperfections, such as a molecular vacancy or orientational disorder,” explains first author Professor Shoji Yoshida. Capturing each frame took only about two minutes, which allows the results to be reproducible. This also makes the approach more practical as a tool for the semiconductor industry.
“We expect that this technology will help lead the way towards the next generation of organic electronics” senior author Professor Hidemi Shigekawa says. By understanding the effects of imperfections, some vacancies, impurities, or structural defects can be purposely introduced into devices to control their function.

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Researchers have discovered a short-lived form of the famous Higgs boson — subject of a groundbreaking search at the Large Hadron Collider — within an iron-based superconductor. This Higgs mode can be accessed and controlled by laser light flashing on the superconductor at trillions of pulses per second. More