Science in brief

High-stakes tests likely factor in STEM performance gap
A new study finds that performance gaps between male and female students increased or decreased based on whether instructors emphasised or de-emphasised the value of exams.

Sehoya Cotner, associate professor in the College of Biological Sciences at the University of Minnesota in the US, and Cissy Ballen, a postdoctoral associate in Cotner's lab, base their findings on a year-long study of students in nine introductory biology courses. They found that female students did not underperform in courses where exams count for less than half of the total course grade. In a separate study, instructors changed the curriculum in three different courses to place higher or lesser value on high-stakes exams (for example, mid-terms and finals) and observed gender-biased patterns in performance.

"When the value of exams is changed, performance gaps increase or decrease accordingly. As people transition to active learning, they tend to incorporate a diversity of low-stakes, formative assessments into their courses. We think that it is this use of mixed assessment that advantages students who are otherwise underserved in the large introductory science courses," Dr Cotner says.

One in five materials chemistry papers may be wrong
The replicability of results from scientific studies has become a major source of concern.

A new study that compared the results reported in thousands of papers published about the properties of metal organic framework (MOF) materials - which are prominent candidates for carbon dioxide adsorption and other separations - suggests the replicability problem should be a concern for materials researchers, too.

One in five studies of MOF materials examined by researchers at the Georgia Institute of Technology in the US were judged to be outliers, with results far beyond the error bars normally used to evaluate study results. The thousands of research papers yielded just nine MOF compounds for which four or more independent studies allowed appropriate comparison of results.

"At a fundamental level, I think people in materials chemistry feel that things are reproducible and that they can count on the results of a single study," said David Sholl, a professor and John F Brock III School Chair in the Georgia Tech School of Chemical and Biomolecular Engineering. "But what we found is that if you pull out any experiment at random, there's a one in five chance that the results are completely wrong - not just slightly off, but not even close."

Whether the results can be more broadly applied to other areas of materials science awaits additional studies, Sholl said. "The net result is non-optimal use of resources at the very least," Sholl said.

Gotham City provides test case for community resilience
In a new study, civil engineer Dr Hussam Mahmoud of Colorado State University in the US offers an innovative approach to defining resilience that could help communities better prepare for hazards.

Finite element analysis is a mathematical tool that engineers use to assess stresses and strain in structural elements, like beams and columns. Dr Mahmoud's 'hazard-agnostic' finite element resilience model is built on the principle that a community, be it a town, city or suburb, responds to a disaster very much like a swinging pendulum or vibrating violin string responds to a force.

To demonstrate the versatility of their model, the team used the fictional city of Batman, Gotham City, as a test bed.

Typically, resilience is viewed as an engineering, social or economic problem, and individual communities decide which metrics matter most to them. The metrics usually fall into a series of 'lifelines' like water, housing, power, health, community and transportation. In Dr Mahmoud's approach, recovery of all lifelines is integrated to form a unified resilience metric. The metric combines engineering, social and economic features of the lifelines together and simplifies resilience into three classes: social, economic and infrastructure.

Using an equation from classical mechanics, the team considered mass to represent social vulnerabilities; damping to represent funds available for recovery; and stiffness to represent robustness of infrastructure. If one or more of these variables experiences a change, the rest of the system follows suit.

They verified their model using a map of Gotham city and recorded the effects of various 'disasters'. Among their observations was that a fast recovery is not necessarily best; if a community bounces back too quickly from a disruption, it can cause instabilities.

"Our model can help us determine what happens to your community, both spatially and temporally, if it's struck by a natural disaster, economic downturn or social disruption," Dr Mahmoud said.

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