Science

On the march: scientists in Brazil protest cuts to spending Scientists in Brazil have protested devastating cuts to science that are threatening to close institutes and funding agencies across the country. Earlier this month about 900 people took to the streets in Rio de Janeiro to protest over budget reductions that have hit science this year. Meanwhile, around 80,000 people in Brazil have signed an online petition, set up in late August, calling on Brazil’s president, Michel Temer, to reverse the cuts. Brazil spent around R$10bn (£2.4bn) on science in 2014, but that figure has been steadily dropping. This year the budget was initially planned to be around R$6bn, but the new government that took over in August 2016 following the impeachment of Dilma Rousseff slashed it even further to R$3.4m. Major scientific agencies are now starting to run out of money. The National Council for Scientific and Technological Development, for example, may not be …

In a spin: energy levels of a spin-valley half-metal A new type of material called a “spin-valley half-metal” has been predicted by calculations done by physicists in Russia, Japan and the US. While the material has not yet been characterized in the laboratory, the team says it could find use in new types of biocompatible and carbon-based electronics. Half-metals are materials in which only electrons with a specific spin polarization (spin-up, for example) participate in electrical conduction. These materials can therefore create currents with 100% spin polarization. This means that half-metals could be very useful for making spintronic devices – components that use the spin of the electron to store and process information. Strong interactions Materials that are known to be half-metals are compounds containing transition metals such as nickel and manganese. These elements ensure that there are strong interactions between conduction electrons, which result in the spin polarization. However, these metallic compounds are not …

After two decades in space, the Cassini mission will come to a dramatic end today (15 September) as the craft is deliberately hurled into Saturn’s atmosphere, where it will burn up on entry. According to mission scientists, Cassini will continue to collect valuable scientific data throughout this final act, from which we could learn about the planet’s atmosphere. This finale will also avoid the unlikely event that Cassini crashes into one of Saturn’s moons in the future – Titan and Enceladus could both contain habitable environments that could be contaminated by the wreckage. “We’ve all known this day was coming for a long time, but it seems strangely unreal at the moment,” says mission scientist Joshua Colwell. “There’s a community of people associated with this mission that will gradually dissolve, so it’s a sad day for me, but also one to marvel at the voyage and what we’ve learned and still have to learn from the …

Coming together: simulation uses LIGO data to explain black hole binaries A new computer simulation by physicists in the US suggests that interactions between dark matter particles can explain why galaxies with similar masses can have different rotation curves. The cold dark matter (CDM) model assumes that dark-matter particles interact with each other very weakly. When combined with a cosmological constant (Λ) that describes the expansion of the universe, the ΛCDM model is very good at explaining the large-scale structure of the universe. However, CDM is not very good at predicting the distribution of mass within individual galaxies once they have formed. Stronger interactions In 2000 David Spergel and Paul Steinhardt at Princeton University argued that this shortcoming could be eliminated if dark-matter particles interacted more strongly with each other. This has since been dubbed the self-interacting dark matter (SIDM) model. Now, Hai-Bo Yu at the University of California Riverside, Monoj Kaplinghat at the University …

Take off: time sequence of a catapulted object Liquid droplets or soft solid objects can be catapulted with more than twice the energy of rigid projectiles, according to physicists in France. They say that this “super propulsion” relies on additional momentum provided by the stretching and compression of deformation and could have practical applications in areas ranging from ballistics to bioengineering. The effect involves superhydrophobic surfaces, which, like lotus leaves, are very hard to wet. Previously, scientists had shown that liquid droplets can bounce off these surfaces just like elastic balls, and now Franck Celestini of the University of Côte d’Azur in Nice and colleagues have demonstrated that these surfaces can be used to make very effective catapults. The catapult in their case was a tiny upright spring with one end anchored to the ground and the other supporting a metal plate. Initially compressed and held at rest by an electromagnet, the spring undergoes harmonic …

Back to front: simulation showing colliding spiral wave-front and wave-back A mechanism that can break up potentially deadly spiral waves in heart tissue has been identified in simulations done by a team led by Sasha Panfilov at Ghent University in Belgium. Spiral waves can cause irregular heartbeats (arrhythmias) and the team says that the newly discovered mechanism could help stop this potentially deadly condition. The heart is a mechanical pump that is governed by electrical activity. Researchers also know that the mechanical deformation of the heart by external forces can affect its normal operation – a process called mechano-electrical feedback (MEF). Physical impacts to the chest are known to both cause and correct arrhythmias, for example, and impacts can even cause death. Colliding waves The team simulated MEF using a 2D computer model of the electrical and mechanical properties of heart tissue. Spiral waves were initiated in the simulation and then the system was subjected …

Laser pioneer: Nicolaas Bloembergen Nicolaas Bloembergen, the Dutch–American physicist who shared the 1981 Nobel Prize for Physics, has died at the age of 97. Bloembergen died on 5 September following complications arising from a heart attack. Born in Dordrecht, the Netherlands, on 11 March 1920, Bloembergen studied physics at the University of Utrecht. He graduated in 1943 with a Phil. Drs degree – equivalent to an MSc – just before the occupying German forces closed the university during the Second World War. Although he was not Jewish, Bloembergen spent two years in hiding from the Nazis. He later told the Nobel Foundation that during this time he ate tulip bulbs to fill his stomach and read the Dutch physicist Hendrik Kramers’s book Quantum Theorie des Elektrons und der Strahlung by the light of a storm lamp that needed cleaning every 20 minutes. In 1945 Bloembergen moved to Harvard University. Two years later he returned to the Netherlands to …

Sharp turn: how the spin Nernst effect works Spin separation caused by the thermal flow of electrons has been observed by an international team of physicists. Called the “spin Nernst effect”, the phenomenon involves the separation of spin-up and spin-down electrons without the application of a magnetic field. The research could help with the development of new technologies including spintronics – circuits that store and process information using spins – and devices that convert heat into usable electrical energy. The spin Nernst effect is the thermal version of the spin Hall effect, which occurs when electrical currents flow through thin strips made of certain materials. Spin-up electrons will migrate towards one edge of the strip and spin-down electrons towards the opposite edge of the strip. This is the result of the spin–orbit interaction between the intrinsic spin of the electron and the magnetic field created by its motion relative to the ions that make up …

Candid camera: the array of single-photon detectors Scientists in the UK have developed a new technique that uses light to locate objects deep within biological tissue and which could help physicians better diagnose lung diseases. Implemented without bulky equipment and in the glare of fluorescent lighting, the technique involves precisely measuring how long it takes single photons to leave the body after being sent down a fibre-optic extension of an endoscope. The research has been carried out as part of the Proteus project, in which more than 40 scientists from three different universities – Edinburgh, Bath and Heriot-Watt – are working together to better observe bacteria in lungs. Doctors look inside lungs using endoscopes – long narrow tubes that they insert into the lung’s airways and which they guide using a lensed camera built into the device. However, as Michael Tanner of Heriot-Watt explains, endoscopes are usually more than a centimetre in diameter, which means …

Looking up: the Canadian Hydrogen Intensity Mapping Experiment uses a unique “half-pipe” design Canada has finished the construction of the country’s largest radio telescope. The C$16m Canadian Hydrogen Intensity-Mapping Experiment (CHIME) near Penticton, British Columbia, is the first research telescope to be built in Canada in more than 30 years. A ceremony to mark the completion of the telescope was attended yesterday by Canadian science minister Kirsty Duncan. CHIME is located at the National Research Council of Canada’s Dominion Radio Astrophysical Observatory, which is about 260 km east of Vancouver. The observatory boasts four 100 m-long u-shaped cylinders of metal mesh and collects radio waves with wavelengths between 37–75 cm – similar to the wavelength used by mobile phones. Signals collected by the CHIME telescope will be digitally sampled nearly one billion times per second, then processed to produce an image of the sky. Bizarre bursts Astronomers will use the telescope to map a quarter of the observable universe …

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