>Super Tuesday 2020 results
The Democratic party's presidential field, which featured more than a half-dozen candidates a week ago, transformed into a two-man contest.
A resurgent Joe Biden scored victories from Texas to Massachusetts on Super Tuesday, revitalizing a presidential bid that was teetering on the edge of disaster just days earlier.
But his rival Bernie Sanders seized the biggest prize with a win in California that ensured he would drive the Democrats' nomination fight for the foreseeable future.
Biden drew support from a broad coalition of moderates and conservatives, African Americans and voters older than 45.
Sanders' success was built on a base of energized liberals, young people and Latinos.
But he was unable to sufficiently widen his appeal to older voters and college graduates who make up a sizable share of Democratic voters, according to AP VoteCast.
>Arctic may see 'ice-free' summers
A study suggests that the Arctic "may be essentially ice-free during summer within 15 years."
The study used statistical models to predict the future amount of Arctic ice, which suggested that the Arctic could be ice-free in the summer during the decade of the 2030s – most likely in the year 2034.
Sea ice is frozen ocean water that melts each summer, then refreezes each winter.
The amount of summer sea ice in the Arctic has been steadily shrinking over the past few decades because of global warming.
It reached its second-smallest level on record in 2019, the National Oceanic and Atmospheric Administration said.
What scientists refer to as the first "ice-free" Arctic summer year will occur when the Arctic has less than 1 million square kilometers of sea ice.
>Carriers restart flights
Chinese carriers have started resuming some of their domestic and international services that were suspended due to the novel coronavirus outbreak.
"Our services have been growing steadily since Feb 21. We expect more than half of the suspended flights to be operational by the middle of this month," said Zhang Wu'an, spokesperson of budget carrier Spring Airlines.
China Eastern Airlines, China Southern Airlines and Air China are also restoring their domestic and international flights.
Industry experts said the novel coronavirus outbreak dealt a great blow to the aviation sector, but the market will see a strong rebound after the country brings the epidemic under control.
>Scientists find virus mutations
Chinese scientists found that the coronavirus causing COVID-19 has two mutations, S-cov and the more dangerous L-cov, that features higher transmissibility and inflicts more harm to the human respiratory system.
By analyzing the genome-wide molecular evolution of 103 novel coronavirus samples, scientists from Peking University's School of Life Sciences and Institut Pasteur of Shanghai, Chinese Academy of Sciences found 101 samples that can be categorized into S-cov and L-cov based on 149 mutation spots on virus strains.
The research was published Tuesday in the National Science Review.
The paper states that S-cov, accounting for 30%, is closer to the bat-related coronavirus and is relatively older, while the L-cov was more prevalent in the early stages of the outbreak in Wuhan but declined in early January.
Most patients were infected with only one of the two variants.
But a sample from an American patient who had recently traveled to Wuhan suggested he might have been infected with both.
Scientists say the possibility of a third mutation cannot be ruled out.
Medical experts said there might be more variants discovered as infections spike globally, since the mutation occurs from the virus adapting to different environments and hosts.
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