The uniqueness of gold and its appreciation as a valuable throughout history is closely related to its exceptional stability to chemical reactions and extreme pressures and temperatures. Gold was considered as a synonym of immovability and constancy (remember the wedding rings!). Indeed, at ambient pressure gold has been known to remain stable in a cubic crystalline phase to at least 180 GPa (one million eight hundred thousand atmospheres).
Scientists from the Bayerisches Geoinstitut and the University of Heidelberg (Germany), together with researchers from Sweden and the ESRF (France) have detected for the first time a phase transformation in gold using the synchrotron. The experiments have shown that at pressures above ~240 GPa gold adopts an hexagonal-close packed structure.
In order to carry out their experiments, scientists used two beamlines of the ESRF combined with a new instrument at the Bayerisches Geoinstitut. The sample was placed inside a diamond anvil cell, which was then electrically heated externally. This allowed them to study gold at the pressures of the Earth’s core, that is, at a depth of 5500 km from the surface.
Advances in high-pressure techniques require standards which are applicable at a multimegabar pressure range. Large pressure and temperature stability of the cubic gold phase and its high isothermal compressibility make gold an ideal material to be used as a pressure marker at high pressure- high temperature experiments at pressures above 100 GPa. The pressure-induced phase transition found in gold at pressure above 240 GPa places a “natural” limit on the application of cubic gold as a standard.
These results confirm the theoretical predictions about the phase changes in gold. “These new experimental and theoretical results remind us that there is no “absolute” unchangeable material, and the noblest of all metals, gold, is not an exception from this rule”, explains Leonid Dubrovinsky, main researcher.
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Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
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Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
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Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
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For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
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