New patterns of partnership are emerging among scientific powerhouses.

Why it matters: International collaborations tend to yield impactful scientific advances — but there is intense political debate in the U.S. and beyond about the calculus of maximizing those benefits while minimizing the national security concerns collaborations can bring.

By the numbers: The overall share of science and engineering publications from international teams climbed from 16% in 2003 to nearly 23% in 2022, according to the latest National Science Board's Science & Engineering Indicators released this week.

• Over those two decades, China and the U.S. became each other's most frequent scientific partners. That remains true though data indicates collaborations between the two countries began to decline in 2020 for the first time in decades.
• China generated the most scientific publications in 2022 — about twice as many as the U.S. The share of articles from China that were highly cited grew from 0.4% in 2006 to 1.3% in 2020, while the share of U.S. articles that were highly cited dropped to 1.7% in 2020 and Japan slipped as well.
• The data echoes another recent analysis from Clarivate, which noted: "China has moved strongly ahead and has effectively dispelled the notion that China emphasizes quantity above quality."
• No one country leads in all scientific areas — for example, the U.S. published the most papers in the health sciences, China in engineering, and India in computer science.

Zoom in: The network of publications on artificial intelligence — deemed a critical technology by the Biden administration and leaders the world over — is centered on the U.S. and China.

• About 33% of U.S. publications in AI-related fields between 2003 and 2022 were the result of international collaborations, compared to 16% of China's AI papers.
• As in other fields, the U.S. and China are one another's main partners. The next 10 most prolific partnerships between countries involve one of them.

Between the lines: Beyond the main partnerships, research is often regionalized — clustered in Europe, Asia and other places where there is historical cooperation, political and economic alignment or simply opportunity.

• China has increased its focus on the Silk Road region, partnering with Saudi Arabia, Pakistan and Egypt, as well as Singapore and other countries in Asia. Researchers in India are working with their counterparts in Australia.
• Those partnerships make sense, says Jonathan Adams, chief scientist at the Institute for Scientific Information at Clarivate, which also found China is looking beyond the U.S. for science partners. It can be difficult for countries that are building their scientific capabilities to break into a longstanding network of collaborations between countries and institutions, he says.
• But the regionalization also reflects geopolitics, says Joy Zhang, a sociologist at the University of Kent in the UK, who adds it isn't something to necessarily worry about but to watch.
• "We're in an age where innovation only happens when you keep knowledge circulating," she says. "Knowledge is no longer an asset if it's just sitting there."

The overall trend in science is more collaboration. China has signed at least 52 science and technology agreements (STA) with other countries and other science-related agreements with 64 other countries, according to a recent study.

• The U.S. has nearly 60 bilateral STAs.
• A longstanding agreement between the U.S. and China — which expired in August — was extended and is being renegotiated.

Yes, but: China and India still have a strong domestic focus, according to the data.

• About 20% of publications from researchers in China and 24% of those authored by scientists in India involved international collaborations compared to 40% for the U.S. and 67% for the U.K.
• China and India should be concerned, Zhang says, because while they are rising science powers, they're "still in this model of keeping everything domestic and that's not efficient."

The debate: U.S. policymakers are debating what guardrails might be placed on science and tech collaborations, including immigration measures, to address those concerns.

• Other experts argue international scientific collaborations are a key window into the advances and capabilities of other countries.
• They are "our best hope for avoiding technological surprise," says Suresh Garimella, president of the University of Vermont and a member of the National Science Board.

The big picture: "The risk isn't that there is a different center but that there is no center," says Deborah Seligsohn, a professor of political science at Villanova University.

• Periods of great scientific advancement have usually had a center where scientists could freely exchange ideas, she says, pointing to ancient Athens, Germany before the world wars of the 20th century, and the U.S. since.
• "For the last 100 years, the place where people felt most free to pursue their research and funding is most plentiful is the U.S."

Scientists this week published a complete atlas of the cells in the mouse brain — a feat researchers hope will help to reveal the cellular basis of brain disorders and provide new details about the evolution of the brain.

Driving the news: Researchers combined information about the genes being expressed in cells and other properties to create a high-resolution map of cells in the mouse brain.

• They found 5,322 types of cells and mapped their locations throughout the brain.
• The results were published in 10 papers this week.

What they're saying: "This kind of a cellular and circuit level investigation of how things change in disease really holds the key to understand what's happening in disease and to develop targeted treatment," says Hongkui Zeng, director of the Allen Institute for Brain Science and co-author of some of the papers.

The intrigue: The researchers found "surprising" differences in the cell types in different parts of the brain, Zeng says.

• The ventral part of the brain — the hypothalamus, midbrain and other more ancient parts — has numerous types of cells that are all similar to one another.
• The dorsal region — the cortex and other newer parts of the brain — have a smaller number of cell types but the types were more different from one another compared to those in the ventral part of the brain.

What's happening: The old part of the brain carries out survival functions — breathing, blood pressure control, feeding and social instincts like fear.

• The researchers hypothesize that because any changes to these functions could be detrimental to the animal, the small cellular circuits that control processing in this region haven't changed much over time, Zeng says.
• The ventral part is newer and governs adaptive functions — for example, learning and making decisions. The cell types there are very different from one another and the region has "changed dramatically in evolution," Zeng says.

Context: The map is the product of the Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative Cell Census Network (BICCN) — a $375 million National Institutes of Health initiative that spanned five years and involved 250 researchers.

• It is an addition to a growing number of other cell atlases that aim to map different species, including monkeys, mice, humans and other species — underscoring the need to standardize the data among the projects, Nature notes.
• In October, scientists published a census of the cells in the human brain.

The average temperature in the Arctic this summer was the warmest on record, per a report released this week by the National Oceanic and Atmospheric Administration, Axios' Sareen Habeshian writes.

Why it matters: "Extreme weather and climate events during the past year in the Arctic and elsewhere have brought unambiguous, climate change-supercharged impacts to people and ecosystems," the 2023 Arctic Report Card states.

• "The presence or absence of sea ice and the timing of Arctic sea ice cover are major factors in modulating ecosystem and human activity."

The big picture: The peer-reviewed report, which is the work of 82 authors from 13 countries, found it was the Arctic's sixth-warmest year on record overall and sea ice extent continued to decline.

• The average surface air temperature in the Arctic this past year was 20°F — the sixth warmest since 1900.
• The summer average temperature was 43°F.

Yes, but: There were significant regional differences, including a colder-than-normal spring in Alaska that slowed snowpack and sea-ice melt.

• Parts of Canada experienced the highest spring average temperatures on record.

Details: The highest point on Greenland's ice sheet experienced melting for only the fifth time in the 34-year record.

• North American snow cover saw a record low in May this year, while snow accumulation during the 2022-2023 winter was above average in both North America and Eurasia, per the report.
• Precipitation also broke records across different parts of the Arctic, which is on trend toward a wetter Arctic.
• There were, however, some variations such as a dry summer in northern Canada, contributing to record wildfires.

Between the lines: "These changes that are happening, they're more than the graphs and the figures that we see," Susan Natali, a senior scientist at the Woodwell Climate Research Center who was not involved in the NOAA report, told the New York Times.

• "They're having a very severe impact on people's health and ability to travel and ability to access subsistence resources and Indigenous ways of living," added Natali, who also leads the Permafrost Pathways initiative.

Scientists pinpoint cause of severe morning sickness (Azeen Ghorayshi — NYT)

Why scientists are making transparent wood (Jude Coleman — Knowable)

The story of the Indigenous wool dog (Devon Bidal — Hakai)

Astronomers have spotted what might be the smallest "failed star" detected to date.

Details: A team of astronomers found the brown dwarf in the young 5 million-year-old star cluster IC 348, which is about 1,000 light-years away from Earth, they report this week in the Astronomical Journal.

• The brown dwarf — "objects that straddle the dividing line between stars and planets" — is just three to four times more massive than Jupiter, ESA said in a statement. It was detected with the JWST.
• These objects form when they become dense enough that they collapse under their own gravity — but they "never become dense and hot enough to begin fusing hydrogen and turn into a star," per the statement.

The big picture: "One basic question you'll find in every astronomy textbook is, what are the smallest stars? That's what we're trying to answer," Kevin Luhman of Pennsylvania State University and a lead author of the study describing the object said in the statement.