The mixture they study shares properties of many everyday materials -- like toothpaste, saliva, blood, and cell cytoplasm -- which do not fall into the standard textbook cases of solid, liquid, or gas. Instead, these "viscoelastic" materials can have the viscous behavior of a fluid or the elastic behavior of a solid, depending on the situation. The results of these experiments, which are published in the current issue of the journal Physical Review Letters and are featured on its cover, provide new insights into how such materials switch over from being solid-like to being liquid-like.
"As a child will swish its finger through an unknown liquid to find out what it is, we built an experiment to pull a cylinder through this viscoelastic material, to learn how it responds," explains Andrew Belmonte, associate professor of mathematics at Penn State and a member of the research team. Their study revealed experimentally, for the first time, the response of a viscoelastic material to increasingly extreme conditions of flow. "We found that flow happens at slow speeds, cutting happens at intermediate speeds, and tearing happens at the highest speeds," says Joseph R. Gladden, a co-author of the research paper, who collaborated on the study while he was a postdoctoral scholar at Penn State. The researchers also found that the viscoelastic material heals in the wake of the tear, as a torn solid would not, and recovers completely after several hours. "Surprisingly, the strength of the material when it acts like a solid is essentially the same as its surface tension as a liquid. This fact reconnects our understanding of these materials between the extremes of flow and fracture," said Belmonte.
The research received support from the National Science Foundation.
Barbara K. Kennedy | EurekAlert!
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The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
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Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
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The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
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