Cities have long been likened to organisms, ant colonies, and river networks. Yet clever analogies fail to capture the essence of how cities really function.  

A paper in Science attempts to derive a series of mathematical formulas that describe how cities' properties vary in relation to their population size, and then posits a unified, quantitative framework for understanding how cities function and grow. The resulting theoretical framework predicts dozens of statistical relationships observed in thousands of real cities around the world for which reliable data are available.

The Van Allen radiation belts in in the Earth's upper atmosphere, two doughnut-shaped rings of highly charged particles, were discovered in 1958. The Van Allen radiation belts consist of an inner ring of high-energy electrons and energetic positive ions, and an outer ring of high-energy electrons.  

But then in February of this year, a team of scientists writing in Science reported a previously unknown third radiation ring, which circled the Earth between the inner and outer rings in September 2012 and then almost completely disappeared.  

How did this temporary radiation belt appear and dissipate?

Arp 142 looks like the profile of a celestial bird but its imagery shouldn't overlook the fact that close encounters between galaxies are a messy business.

The interacting galaxy duo Arp 142 contains the disturbed, star-forming spiral galaxy NGC 2936, along with its elliptical companion, NGC 2937.

Once part of a flat, spiral disk, the orbits of the galaxy's stars have become scrambled due to gravitational tidal interactions with the other galaxy. This warps the galaxy's orderly spiral, and interstellar gas is strewn out into giant tails like stretched taffy.

The Red Queen hypothesis, a popular idea in evolution named after Lewis Carroll's character who in "Through the Looking Glass" described her country as a place where "it takes all the running you can do, to keep in the same place", recently got studied by a group of researchers who were thinking beyond the death of individual species -  they examined how the lack of new emerging species also contributes to extinction. 

Environmental brochures highlight fears about groups of animals, such as frogs or the "big cats," going extinct. But in science that is only part of the story.

Chlamydia trachomatis is a human pathogen that is the leading cause of bacterial sexually transmitted disease worldwide.

More than 90 million new cases of genital infections occur each year. About 70 percent of women infected with Chlamydia remain asymptomatic and these bacteria can establish chronic infections for months and even years. Even when it causes no symptoms, Chlamydia can damage a woman's reproductive organs but standard antibacterial drugs are proving increasingly ineffective in complete eradication, as Chlamydia goes in to persistent mode, leading to asymptomatic chronic infection.

A student who shows up on time, listens respectfully and appears fully engaged to teachers might still lack emotional and cognitive involvement with the course material, according to survey results

More importantly for educators, the paper in Learning and Instruction suggests that student engagement—essential for success in school—is malleable, and can be improved by promoting a positive school environment. The result may lead to diagnostic tools for recognizing disengagement, as well as strategies for creating a school environment more conducive to student engagement.