Faculty research

Mix two parts cornstarch and one part water and you’ve got a fluid that exhibits shear thickening behavior. (Photography by Andrew Curran, CC-BY-ND 2.0)

Faculty research

Researchers investigate the mystery of shear thickening liquids, harness quantum entanglement, measure the benefits of a guaranteed work program in India, and say “good job!” to process praise.

The plot thickens

If you’ve ever played with oobleck—a goopy mixture of cornstarch and water—you’ve seen that certain fluids, when mixed at high speeds, become so viscous they’re nearly impossible to stir. Scientists have been trying to understand this phenomenon, called shear thickening, for decades, because it may reduce the energy consumption in many industrial processes. One theory? A phenomenon called order-to-disorder transition might be the cause. In order-to-disorder transition, particles arrange themselves neatly at low speeds and become disordered at high speeds. But there was a problem: researchers only observed this transition in some shear thickening liquids. Using an advanced X-ray technique, a team of scientists at Argonne National Laboratory determined that order-to-disorder transition and shear thickening are two separate phenomena. The results, published January 9 in Physical Review Letters, bring scientists one step closer to solving the shear thickening mystery.

Quantum force

It sounds like science fiction, but scientists are more and more confident that quantum entanglement—a force that links two objects, no matter how far apart they are—really exists. Now, in a paper published April 25 in Nature, a group of researchers, including Aashish Clerk, professor in the Institute for Molecular Engineering, have managed to link the motion of two aluminum plates about 20 microns across. They achieved this quantum feat using a custom-designed circuit made out of a superconducting metal. The plates are about the diameter of a human hair, making them among the largest objects scientists have yet entangled. By harnessing the property of quantum entanglement, scientists hope to develop more powerful sensors and computers.

No downsides

Almost one in four adults in India participates in a program that guarantees them 100 days of paid employment on public works projects. It’s a boon to struggling rural communities, but some policy makers worry that the program, established in 2006, dissuades families from educating their children, thereby harming India’s long-term economic growth. In a Becker Friedman Institute working paper released in May, Anjali Adukia, assistant professor at Harris Public Policy, lays those fears to rest. The employment program isn’t associated with a substantial decline in children’s education, Adukia found.

Great job!

How you praise toddlers can affect their performance in school years later, according to researchers including Susan Goldin-Meadow, the Bearsdley Ruml Distinguished Service Professor in Psychology, and Susan Levine, the Rebecca Anne Boylan Professor in Education and Society. Previous research has shown that children who as toddlers received a high proportion of “process praise”—praise that focuses on effort (“you worked hard”), not innate ability (“you’re so smart”)—had more motivation for challenging tasks in school during second and third grade. By fourth grade, according to the new study published in Developmental Psychology in March, these children also had greater achievement in math and reading comprehension.