Could engineers have known ahead of time exactly how much pressure the levees protecting New Orleans could withstand before giving way? Is it possible to predict when and under what conditions material wear and tear will become critical, causing planes to crash or bridges to collapse? A study by Weizmann Institute scientists takes a new and original approach to the study of how materials fracture and split apart.
When force is applied to a material (say, a rock hitting a pane of glass), a crack starts to form in the interior layers of that material. In the glass, for example, the force of the striking rock will cause the fracture to progress through the material with gradually increasing speed until the structure of the glass splits apart. The path the forming crack follows and the direction it takes are influenced by the nature of the force and by its shape. As cracking continues, microscopic ridges form along the advancing front of the crack and the fracture path repeatedly branches, creating a lightning bolt or herringbone pattern.
Physicists attempting to find a formula for the dynamics of cracking, to allow them to predict how a crack will advance in a given material, have faced a serious obstacle. The difficulty lies in pinning down, objectively, the fundamental directionality of the cracking process: From any given angle of observation or starting point of measurement, the crack will look different and yield different results from any other. Scientists all over the world have experimented with cracking but, until now, no one has successfully managed to come up with a method for analyzing the progression of a forming crack.
Elizabeth McCrocklin | EurekAlert!
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Stopping problem ice -- by cracking it
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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.
A warming planet
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.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
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!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
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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22.09.2017 | Physics and Astronomy