Science Daily July 23, 2018 Researchers at Harvard University designed and built a new organic compound called Methuselah molecule that can store electrical energy and has a very long life before it decomposes. In experiments in their laboratories the molecule had a fade rate of less than 0.01 percent per day and less than 0.001 percent per charge/discharge cycle — which extrapolates to less than 3 percent degradation over the course of a year — and useful operation for tens of thousands of cycles. The molecule also proved highly soluble, meaning it can store more energy in a smaller space. […]
A phonon laser operating at an exceptional point
Phys.org July 20, 2018 Exceptional points (EP) are singularities in the energy functions of a physical system at which two light modes coalesce to produce unusual effects. Understanding the mechanisms responsible for linewidth broadening will enable laser resources with new capabilities. An international of researchers led by the US used an optomechanical system with two coupled silica whispering-gallery-mode microresonators to exploit the interplay between gain and loss to tune a phonon laser to an EP. The team provided direct experimental evidence to show complete overlap of optical supermodes at EP, and that EP-enhanced optical noise can be transferred directly to […]
Protecting autonomous grids from potentially crippling GPS spoofing attacks
Science Daily July 19, 2018 Knowing the speed at which electricity moves, the distance between sensors, and the time it takes an oscillation to move between sensors, one can determine whether the oscillation is real. Phasor measurement units (PMUs) allow synchronous real-time measurements of voltage, phase angle, and frequency from multiple remote locations in the grid, enabled by their ability to align to (GPS) clocks. A team of researchers in the US (Clemson University, UC Santa Clara) proposes a distributed real-time wide-area oscillation estimation approach that is robust to GPS spoofing on PMUs and their associated phasor data concentrators. The […]
Researchers charge quest to end ‘voltage fade’
Nanowerk July 23, 2018 An international team of researchers (USA – Cornell University, UC San Diego, Argonne National Laboratory, industry, China, Germany) identified nanoscale defects or “dislocations” in Lithium-rich NMC cathode materials as they charged batteries at a range of voltages going up to 4.4 volts. They demonstrated that heat treating the cathode materials eliminated most of the defects and restored the original voltage showing that voltage fade had been reversed. According to the researchers while heat treating is not scalable, the physics and materials science-based approach to characterizing and then addressing the nanoscale defects offers promise for finding new […]
Researchers move closer to completely optical artificial neural network
Eurekalert July 19, 2018 There is interest in using integrated optics as a hardware platform for implementing artificial neural networks. However, currently on the integrated photonics platform there is no efficient protocol for the training of these networks. Researchers at Stanford University have developed a method that enables highly efficient, in situ training of a photonic neural network by using adjoint variable methods to derive the photonic analogue of the backpropagation algorithm. As demonstration they trained a numerically simulated photonic artificial neural network. The method may be of broad interest to experimental sensitivity analysis of photonic systems and optimization of […]
Reversing cause and effect is no trouble for quantum computers
Phys.org July 20, 2018 When physics does not impose any direction on time, where does causal asymmetry—the memory overhead needed to reverse cause and effect—come from? An international team of researchers (Singapore, UC Davis, UK, Austria) has shown that quantum models forced to run in the less-natural temporal direction not only surpass their optimal classical counterparts but also any classical model running in reverse time. This holds even when the memory overhead is unbounded, resulting in quantum models with unbounded memory advantage. According to the researchers the models that use quantum physics can entirely mitigate the memory overhead. Doing away […]
Scientists develop new materials that move in response to light
Phys.org July 24, 2018 A team of researchers in the US (Tufts University, Los Alamos National Laboratory) has developed magnetic elastomeric composites that move in different ways when exposed to light. The flexible material composites, when illuminated, are capable of macroscale motion, through the interplay of optically absorptive elements and low Curie temperature magnetic materials. These composites can be formed into films, sponges, monoliths, and hydrogels, and can be actuated with light at desired locations. They demonstrated the versatility of the material for gripping and releasing, heliotactic motion, light-driven propulsion, and rotation… read more. TECHNICAL ARTICLE
Scientists use excitons to take electronics into the future
Nanowerk July 25, 2018 An international team of researchers (Switzerland, Japan) made excitonic devices made of MoS2–WSe2 van der Waals heterostructures encapsulated in hexagonal boron nitride that demonstrate electrically controlled transistor actions at room temperature. The long-lived nature of the interlayer excitons in the devices results in them diffusing over five micrometres. Within the device, they have demonstrated the ability to manipulate exciton dynamics by creating electrically reconfigurable confining and repulsive potentials for the exciton flux. The research shows that it will be possible to integrate optical transmission and electronic data-processing systems into the same device, which will reduce the […]
A single photon detection system for the spectrum range up to 2300 nm
Arxiv July 11. 2018 An international team of researchers (Russia, Poland) has demonstrated niobium nitride based superconducting single-photon detectors are sensitive in the spectral range 457 nm – 2300 nm. The system performance was tested in a real-life experiment with correlated photons generated by means of spontaneous parametric down conversion, where one of photon was in the visible range and the other was in the infrared range. They measured a signal to noise ratio as high as 4×104 in their detection setting. A photon detection efficiency as high as 64 % at 1550 nm and 15 % at 2300 nm […]
A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
Phys.org July 20, 2018 Reversible sol-gel transition hydrogels are normally in flowing liquid state at or below room temperature and can transform into stationary gels when heated above a critical temperature and transition can be reversed after cooling down. Researchers in China synthesized a temperature-sensitive sol-gel transition electrolyte comprising proton-incorporated poly(N-isopropylacrylamide-co-acrylic acid) (PNA) incorporating it into a rechargeable Zn/α-MnO2 battery system. After heating above the low critical temperature, a gelation process occurs in the PNA sol-gel electrolyte shutting down the battery. After cooling down, the transition is reversed to liquid state and an original electrochemical performance can be restored. Because […]