1 . High-resolution (高分辨率) satellite imagery has been used to map every single tree in Africa, showing a technique that could help improve the monitoring of deforestation (森林砍伐) across the world. Florian Reiner at the University of Copenhagen, Denmark, and his colleagues used images from sate lies to map canopy (树冠) across the entire African continent.

Modern sate lies usually catch tree canopies at a resolution of 30 meters — fine for measuring the size of forests, but less good at mapping individual trees. The satellite data Reiner and his colleagues used had a resolution of 3 meters, enabling the study to map all trees, including those not part of a forest.

The results suggest that 30 percent of all trees in Africa aren’t in a forest and instead are across farmland, savannah and urban areas. “Many countries in Africa lack thick forests, but have a lot of trees.” says Reiner. “These trees are extremely important to the local ecosystems, the people and the economy. By tracking every single tree, researchers can start to monitor how these trees are coping with climate change or whether they are sensitive to deforestation.” It could also improve the monitoring of reforestation efforts, which are growing in popularity as a way of removing carbon dioxide from the atmosphere.

“At a local level, being able to consistently monitor when and where trees are disappearing or reappearing can lead to more actionable insights,” says John Francis at the Alan Turing Institute in London.

“The study is a proof of concept rather than a map ready for immediate commercial use,” says Reiner. “It’s research work. It’s showing what could be done,” he says. But he is already working with colleagues to scale up the tracking approach to cover the entire global canopy: “We’re hoping that this will be seen as a way forward in monitoring tree resources.”

2 . Every language and culture has curse words (脏话). What gives a curse word its power is partly its meaning and partly its sound. “In English, for example, curse words tend to contain a high percentage of plosive sounds—including P, T and K,” said Ryan McKay, a psychologist at University of London.

Dr. McKay teamed up with his colleague Shiri Lev-Ari to learn whether this familiar pattern went beyond English. They wondered whether it might even represent what’s called sound symbolism. Sound symbolism is when a word sounds like what it means.

The researchers first asked fluent speakers of Hebrew, Hindi, Hungarian, Korean and Russian to list the most vulgar (粗俗的) words they could think of. Once they’d made a list of each language’s most frequently used curse words, the researchers compared these with neutral words from the same language. In these languages, they didn’t find the plosive sounds that seem common in English curse words. “Instead, we found that the vulgar words were defined by what they lacked: the approximant sounds that include letters I, L, R, W and Y, ”Dr. Lev-Ari said.

Next, the scientists invited 215 native speakers of six languages: Arabic, Chinese, Finnish, French, German and Spanish. The participants listened to pairs of words in a language they didn’t speak, and guessed which word in each pair was offensive. In reality, all the words were invented. For example, the researchers started with the Albanian word “zog, ” for “bird, ”and created the pair of fake words “yog" and “tsog. ”Participants were more likely to guess that words without approximants, such as “tsog, ” were curses.

Finally, the researchers combed through the dictionary for English curse words and their cleaned-up versions. Once again, the clean versions included more of the sounds I, L, R, W and Y.

A 20th-century linguistic (语言学的)principle claimed that the sounds of words were arbitrary: Any word could have any meaning. With curse words, though, as in other cases of sound symbolism, “the sounds themselves seem to carry meaning, ”said Lev-Ari. “That’s a new thing, ”said linguist Benjamin Bergen. “Curse words across languages, unrelated to each other, may pattern similarly. ”He also pointed out, to make sure the pattern of approximants missing from curses isn’t an accident, it would be nice to find it in an even larger sample of languages.

4 . As Alexandria Country Day School’s sixth-graders created miniature 3D printed villages to address homelessness, they learned lessons far beyond technology.

“It Takes a Village” began as a project for a science class, inspired by life-size 3D-printed homes built by Austin, Texas-based technology company Icon.

No strangers to classroom 3D projects, the students were fascinated by Icon’s use of a similar process to create homes made of inexpensive concrete-like material. Unlike standard construction methods, the process of building these durable homes takes just a few days.

While creating their mini 3D buildings, the students explored how such technology allows design freedom and quick changes. Mathematical conversions helped get the relations right. For example, a real 25-foot-by-20-foot one-bedroom house would be printed as 40-millimeter-by-32-millimeter (about 1 1/2 inch by 1 1/4 inch) for their mini village. Salwa Seman, 11, said that getting the dimensions and settings correct before construction began was challenging as she created a curved-wall amphitheater (圆形剧场).

The tech-focused project quickly evolved into “an exercise in empathy (共情), innovation and cooperation designed to bring about lasting change”. “When most people think of helping the homeless, they think of food and clothing drives,” said Juliet Galicia, 11. “While necessary, those are temporary fixes. Even housing by itself is not a complete solution.”

In designing their leave-homelessness-behind neighborhoods, priorities were shelter, food stores, schools, and health centers. But to build a sense of belonging and purpose, the miniature communities also emphasized areas for frequent interaction among residents. “We wanted to make it feel more like a real community,” said Luke Wazorko, 11. A community garden, a place to raise chickens, an amphitheater for shared events, bus stops for access to jobs, and infrastructure for Wi-Fi and cellphones to help in job searches were important features to offer formerly unhoused residents.

Amber Fogarty, president of a nonprofit organization tackling homelessness in Austin, said, “Housing alone will never solve homelessness, but community will. People need a place where they are known, cared for and loved.”

5 . Like a phoenix (凤凰), some stars may burst to life covered in “ash,” rising from the remains of stars that had previously passed on.

Two fireballs covered in carbon and oxygen, ashy byproducts of helium fusion (氦聚变), belong to a new class of stars, researchers report in the March Monthly Notices. Though these burning objects are not the first stars found covered in carbon and oxygen, they are the first discovered to have helium-burning cores.

“That merger (并合) tells you the star must have evolved differently,” says study author Nicole Reindl.

The stars may have formed from the merger of two white dwarfs (白矮星), the remaining hearts of stars that exhausted their fuel, Reindl further explains. One of the two was rich in helium, while the other contained lots of carbon and oxygen. These two white dwarfs had already been orbiting one another, but gradually drew together. Eventually the helium-rich white dwarf “ate” its partner, leaving carbon and oxygen all over its surface, just as a messy child might get food all over their face.

Such a merger would have produced a star covered in carbon and oxygen to burn nuclear fusion in its core again, says Tiara Battich, a German astrophysicist.

To test this idea, Battich copied the evolution, death and eventual merger of two stars on his computer and simulated (模拟) the process. He found that putting together a carbon-and-oxygen-rich white dwarf and a more massive helium one could explain the compositions of the two stars observed by Reindl and her colleagues.

“But this should happen very rarely,” Battich says. In most cases the opposite should occur, because carbon-oxygen white dwarfs are usually the more massive ones. For the rarer case to occur, two stars slightly more massive than the sun must have formed at just the right distance and the right time.

"The origins story Battich proposes demands a very specific and unusual set of circumstances, " says Simon Blouin, a Canadian astrophysicist. “But in the end, it makes sense.”