Science

Cosmological noise: signals from both LIGO detectors Correlated noise in the two LIGO gravitational-wave detectors may provide evidence that the universe is governed by conformal cyclic cosmology (CCC). That is the claim of Roger Penrose of the University of Oxford, who is proposing that the apparent noise is actually a real signal of gravitational waves generated by the decay of hypothetical dark-matter particles predicted by CCC. Last month, physicists at the Niels Bohr Institute pointed out that some of the noise in the two LIGO detectors appears to be correlated – with a delay that corresponds to the time it takes for a gravitational wave to travel the more than 3000 km between the instruments. Writing in a preprint on arXiv, Penrose argues that a significant amount of this noise could be a signal of astrophysical or cosmological origin – and specifically CCC. Infinite aeons First proposed over a decade ago by Penrose, CCC assumes that …

Medal ceremony: Jocelyn Bell Burnell accepts the President’s Medal from Roy Sambles The astrophysicist Jocelyn Bell Burnell has been awarded the President’s Medal of the Institute of Physics (IOP) “for her outstanding contributions to physics through pioneering research in astronomy, most notably the discovery of the first pulsars, and through her unparalleled record of leadership within the community”. The award, which is given at the discretion of the IOP president, was presented yesterday in Birmingham at the International Conference on Women in Physics. While presenting the award, IOP president Roy Sambles said: “Jocelyn is a groundbreaking researcher, an inspirational leader within our community and a distinguished ambassador for physics – particularly for widening participation.” PhD breakthrough While a PhD student at the University of Cambridge, Bell Burnell discovered the first four pulsars – an achievement that contributed to the awarding of the Nobel Prize for Physics to Antony Hewish and Martin Ryle in 1974. Controversially, …

Language of glove: wearable device translates gestures A smart glove that translates American Sign Language (ASL) into digital text has been developed by scientists at the University of California, San Diego. Timothy O’Connor, Darren Lipomi and colleagues reckon that their device can be produced for less than $100 and could also find use in virtual-reality and remote-control systems. Most systems for monitoring body movement involve using a camera or infrared emitters and sensors to capture motion. While such systems are effective, they can be bulky, inflexible and require large amounts of energy. As a result, researchers are keen to develop wearable motion sensors – and gloves offer a natural way of tracking hand motion. Strain sensors The new device is based on strain sensors that are made of a piezoresistive composite material comprising carbon particles embedded in a flexible material. To make a sensor, the team begins with a strip of silicone 3 cm long, 0.5 cm …

Bubble test: measuring shear in graphene The force needed to slide sheets of graphene across each other has been measured using a new technique that involves blowing air bubbles made of the material. Developed by Zhong Zhang of the National Center for Nanoscience and Technology in Beijing and colleagues in China and the US, the technique was also used to measure the force needed to slide graphene across a surface of silicon dioxide. Graphene is a layer of carbon just one atom thick that has a wide range of potentially useful electronic and mechanical properties. Developing practical graphene-based devices will require an understanding of how well graphene layers stick to each other, and also how they stick to popular substrates such as silicon dioxide. This stickiness is expressed as the shear resistance – the minimum force required to slide one layer over another. This quantity is not well known for graphene because it is extremely …

Phantom head: proton CT images Physicists in the US have shown that protons themselves can be used to provide the complex 3D images essential for tailoring proton therapy to individual patients. Researchers in the US built a prototype detector to carry out “proton computed tomography” (proton CT), and found that in around 6 min it could generate maps of proton stopping power – energy lost per unit distance in a material – that were more accurate and required a much lower radiation dose than existing techniques. Proton therapy is becoming an increasingly popular tool to treat cancer because it can be used to target tumours very precisely. Unlike most other types of radiation, protons deposit a large fraction of their energy at the point where they stop in the body. By tuning the beam so that protons stop where the tumour is located, therapy can be made more effective and safer. To deliver the radiation to …

Ice, ice, baby: rare ice VII is not native to Earth The transformation of water freezing into an exotic type of ice has been directly observed for the first time by researchers in the US. Most of the ice on Earth has a hexagonal crystal structure, but water can transform into more than 15 types of ice, each with a different molecular arrangement. These rare frozen phases require non-atmospheric pressures and controlled temperature environments to form, so can only be produced on Earth in laboratory experiments. One exotic type is ice VII – a cubic crystal phase that can form at high pressure and high temperature. It is thought that this “hot ice” could be found on the ocean floor of Saturn’s moon Titan and other watery exoplanets. Back on Earth, however, it is difficult to create and maintain ice VII in a lab. Previous studies have attempted to “shock freeze” water using lasers to …

Extra light: how a companion star can affect transit measurements A significant number of known exoplanets could have larger diameters than previously thought, according to two astronomers in the US. These exoplanets orbit stars that are in a binary system with another star – and it is light from this companion star that has thrown off previous measurements. The work suggests that some known exoplanets are less dense than previously thought, which means that they resemble Jupiter, rather than Earth. Many of the exoplanets discovered by the Kepler space telescope and other instruments orbit stars in binary systems. It can be difficult to differentiate between the two stars in such systems – which can appear as a single point of light. This is a problem if the exoplanet is studied using the transit method whereby the diameter of the planet relative to that of its star is determined from how much starlight it blocks when …

Cash in hand: Chinese researchers were paid up to $165,000 per paper Chinese researchers were paid an average of $43,000 in 2016 for each paper published in Nature and Science, according to a study by information specialists in China and Canada. Wei Quan from Wuhan University, Bikun Chen at Nanjing University of Science and Technology and Fei Shu at McGill University analysed 168 “cash-per-publication” policies at 100 Chinese universities from 1999 to 2016. The researchers found that Chinese universities offer cash rewards ranging from $30 to $165,000 for papers that are published in journals indexed by Web of Science, with the average amount increasing over the past decade. The largest payouts were for Nature and Science papers, with the average award increasing 67% from $26,212 in 2008 to $43,783 in 2016. Negotiable awards They also note that in some cases the amount of cash available for such papers was “negotiable”. Payments for publication in other …

Tilted cone: the band structure of a type-II Dirac fermion is shown on the right The first experimental evidence of a quasiparticle known as a type-II Dirac fermion has been found by three independent research groups – one based in South Korea and two in China. Two of the groups found signs of the quasiparticle in the crystalline material palladium ditelluride. This could mean that the material is a topological superconductor – a hypothetical material with unique properties that could be useful as components in the proposed technology known as a topological quantum computer. The third group found evidence for type-II Dirac fermions in a similar material called platinum ditelluride. Dirac fermions are subatomic particles with half-integer spin that are not their own antiparticles. Electrons in solids can also exhibit particle-like collective behaviour that can be described in terms of Dirac-fermion quasiparticles, which obey the same physics as their subatomic counterparts. These quasiparticles can exist …

Deep thinkers: Giorgio Sangiovanni, Michael Karolak and Andreas Hausoel A theoretical study of nickel at high temperatures and high pressures suggests that the metal could play a crucial role in generating the Earth’s magnetic field. That’s the conclusion of Giorgio Sangiovanni of the University of Würzburg and an international team, which has done calculations suggesting that the thermal conductivity of nickel is much lower than that of iron under these extreme conditions. The geodynamo model says that the Earth’s magnetic field is created by the flow of liquid iron in the outer core of the Earth. This flow is driven by the convection of heat from the inner core to the mantle. A problem with this model is that the thermal conductivity of iron is predicted to be very high at the relevant pressures and temperatures – and this means that convection should not occur. Crystal structure Compared to some other metals, iron and nickel …

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