Research Roundup: Exoplanet growth, how school shootings affect mental health, bacterial jumping genes

Dec. 27, 2019, 9:13 a.m.

Each week, The Daily’s Science & Tech section produces a roundup of the most exciting and influential research happening on campus or otherwise related to Stanford. Here’s our digest for the week of Dec. 15 – Dec. 21.

Exoplanet growth limited by shrinking atmosphere

Exoplanets rarely grow larger than Neptune because they generally have oceans of magma that absorb their atmospheres, found a study published by collaborating researchers on Dec. 17 in “Astrophysical Journal Letters.”

Researchers’ findings suggest that as a planet gathers more hydrogen gas, its expanding atmosphere interacts with a magma ocean at the surface. As the levels of hydrogen in the atmosphere increase, the pressure buildup allows hydrogen to more readily dissolve into the magma.

The result is that planets’ growth stalls before they reach Neptune’s size, since diminishing the hydrogen levels in the atmosphere prevents planets from growing.

“This work really highlights the need to consider a planet in a more holistic sense: It’s the interaction between the atmosphere and the planet’s interior that is controlling the sizes of planets in this region of parameter space,” geological sciences assistant professor Laura Schaefer told Stanford Earth News. “More and more work is showing that boundaries between different layers of a planet are not necessarily as sharp and distinct as we like to imagine.”

School shootings can negatively impact youth mental health

Exposure to fatal school shootings has lead to poor mental health outcomes, as indicated by increased antidepressant use among affected youth, according to a working paper published on Dec. 16 in “National Bureau of Economic Research.”

“There are articles that suggest school shootings are the new norm — they’re happening so frequently that we’re getting desensitized to them — and that maybe for the people who survive, they just go back to normal life because this is just life in America. But what our study shows is that does not appear to be the case,” Maya Rossin-Slater, a faculty fellow at the Stanford Institute for Economic Policy Research, told Stanford News. “There are real consequences on an important marker of mental health.”

The findings suggested that average rate of antidepressant use increased by 21% for youth under 20 years old living in communities that experienced fatal shootings. The researchers observed no significant effect on antidepressant use for youth exposed to non-fatal shootings.

“When we think about the cost of school shootings, they’re often quantified in terms of the cost to the individuals who die or are injured, and their families,” Rossin-Slater told Stanford News. “Those costs are unfathomable and undeniable. But the reality is that there are many more students exposed to school shootings who survive. And the broad implication is to think about the cost not just to the direct victims but to those who are indirectly affected.”

Technology to detect ‘jumping genes’ in infectious bacteria

A bioinformatics tool to identify “jumping genes” in infectious bacteria has been developed by Stanford researchers and presented in a study published on Dec. 17 in “Cell Host and Microbe.”

“Jumping genes” are genes that randomly move to another location in DNA, and they are typically involved with antibiotic resistance development in bacteria.

The tool, called MGEfinder, uses a compare-and-contrast method to analyze a single bacteria strain against thousands of variants of the same species. By isolating differences between the two, researchers can identify likely “jumping genes.”

“We hope that MGEfinder can help inform these decisions and stop organisms from escaping antibiotics in the future,” medicine and genetics assistant professor Ami Bhatt told SCOPE, Stanford Medicine’s blog.

Contact Derek Chen at derekc8 ‘at’

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