Physicist Mathieu Souzy of the University Twente was enjoying an evening of pasta and board games with several colleagues when the conversation turned to how adding salt to a pasta pot to make it boil faster can leave a white ring on the bottom of the pot. Ever the curious scientists, they wondered about the various factors that would contribute to creating the perfect circular pattern for a salt ring.

“By the end of our meal, we’d sketched an experimental protocol and written a succession of experiments we wanted to try on my youngest son’s small whiteboard,” said Souzy . It all comes down to three factors: the diameter of the particles (grains of salt, in this case), the settling height, and the number of particles released simultaneously, according to a new paper published in the journal Physics of Fluids.

We've previously reported on physicists' longstanding interest in similar phenomena like the " coffee ring effect ," when a single liquid evaporates and the solids that had been dissolved in the liquid (like coffee grounds) form a ring. It happens because the evaporation occurs faster at the edge than at the center. Any remaining liquid flows outward to the edge to fill in the gaps, dragging those solids with it. Mixing in solvents (water or alcohol) reduces the effect as long as the drops are very small. Large drops produce more uniform stains.

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President Donald Trump's flurry of day-one actions included a reprieve for TikTok, the creation of a Department of Government Efficiency (DOGE), an order on social media "censorship," a declaration of an energy emergency, and reversal of a Biden order on artificial intelligence.

The TikTok executive order attempts to delay enforcement of a US law that requires TikTok to be banned unless its Chinese owner ByteDance sells the platform. "I am instructing the Attorney General not to take any action to enforce the Act for a period of 75 days from today to allow my Administration an opportunity to determine the appropriate course forward in an orderly way that protects national security while avoiding an abrupt shutdown of a communications platform used by millions of Americans," Trump's order said.

TikTok shut down in the US for part of the weekend but re-emerged after Trump said on Sunday that he would issue an order to "extend the period of time before the law's prohibitions take effect, so that we can make a deal to protect our national security." Trump also suggested that the US should own half of TikTok.

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As fires spread with alarming speed through the Pacific Palisades region of Los Angeles Tuesday, Jan. 7, a local TV news crew recorded a mountain lion trailed by two young cubs running through a neighborhood north of the fire. The three lions were about three-quarters of a mile from the nearest open space. Another TV crew captured video of a disoriented, seemingly orphaned fawn trotting down the middle of a street near the Eaton Fire in Altadena, her fur appearing singed, her gait unsteady.

Firefighters are still struggling to contain fires in Los Angeles County that have so far destroyed thousands of homes and other structures and left more than two dozen people dead. Fires and the notorious Santa Ana winds that fuel their spread are a natural part of this chaparral landscape.

But a warming world is supercharging these fires, experts say. Climate change is causing rapid shifts between very wet years that accelerate the growth of scrubland grasses and brush, leading to what’s known as “excessive fuel loading,” that hotter summers and drier falls and winters turn into easily ignited tinderbox conditions. The area where the fires are burning had “the singularly driest October through early January period we have on record,” said climate scientist Daniel Swain during an online briefing last week.

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US President Donald Trump swore his oath of office on Monday, ascending yet again to the head of the federal government. As widely expected, he signed a swath of executive orders on his first day, many aimed at upending existing policies and satisfying grievances, whether that's pulling the country out of membership of the World Health Organization or reversing the nation's clean vehicle policies.

The Infrastructure and Investment Jobs Act of 2021 and the Inflation Reduction Act of 2022 were signature pieces of former President Joe Biden's term of office. Among other things, the two bills contained many provisions meant to boost US competitiveness in EV manufacturing and build out publicly funded charging infrastructure.

Specifically, the IIJA included $7.5 billion in funding for charging infrastructure . The National Electric Vehicle Infrastructure and the Charging and Fueling Infrastructure programs were modeled on federal highway funding programs, where the funds are disbursed to state departments of transportation, which then award the money to successful applications. NEVI was meant to create corridors of fast chargers along federal highways, and CFI to build out charging infrastructure in underserved areas.

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On his first day in office, President Trump issued an executive order to withdrawal the US from the World Health Organization , a process that requires a one-year notice period as set out in a 1948 Joint Resolution of Congress .

Trump initially tried to extract the US from the United Nations health agency in July 2020, but the process did not come to completion before he was voted out of office.

At the time, Trump criticized the agency's handling of the COVID-19 pandemic, claimed it was protecting China, and asserted that it was overcharging the US in dues. "China has total control over the World Health Organization despite only paying $40 million per year, compared to what the United States has been paying, which is approximately $450 million a year," Trump said in 2020 prior to issuing the first notice of withdrawal.

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A report from Mark Gurman in Bloomberg makes the very reasonable suggestion that automatic email categorization in Apple Mail, already present since iOS 18 arrived on the iPhone , is coming to Macs and iPads in a few months. The feature should arrive with macOS 15.4 and possibly iPadOS 18.4, both due in April.

Similar to Google's server-side Gmail sorting, which debuted in May 2013 , Apple's Mail app on iOS sorts email into categories: "Primary," "Transactions," "Updates," and "Promotions." Moving an email manually from one category to another generally fixes the categorization for that sender from then on. You cannot create new categories, however, or alter how Apple's sorting functions.

Some may prefer the simplicity of a single scroll of messages, versus having to check four separate inboxes to ensure that nothing got missorted or is more important than the label implies. I've used sorting on iOS and generally found it helpful, though I also use the Filters button in the lower-left corner on iOS to do a double-check of all the mail addressed specifically to me. On a Mac desktop, I'm partial to Mimestream , but that's because all my mail comes through Google/Workspace accounts. I'll be watching to see how Mail's sorting translates to macOS.

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For decades, we have been imaging the surface of Mars with ever-finer resolution, cataloging a huge range of features on its surface, studying their composition, and, in a few cases, dispatching rovers to make on-the-ground readings. But a catalog of what's present on Mars doesn't give us answers to what's often the key question: how did a given feature get there? In fact, even with all the data we have available, there are a number of major bits of Martian geography that have produced major academic arguments that have yet to be resolved.

In Monday's issue of Nature Geoscience, a team of UK-based researchers tackle a big one: Mars' dichotomy, the somewhat nebulous boundary between its relatively elevated southern half, and the low basin that occupies its northern hemisphere, a feature that some have proposed also served as an ancient shoreline. The new work suggests that the edge of the dichotomy was eroded back by hundreds of kilometers during the time when an ocean might have occupied Mars' northern hemisphere.

Close to the edge

To view the Martian dichotomy, all you need to do is color-code a relief map of the Martian surface, something that NASA has conveniently done for us . Barring a couple of enormous basins, the entire southern hemisphere of the red planet is elevated by a kilometer or more, and sits atop a far thicker crust. With the exception of the volcanic Tharsis region the boundary between these two areas runs roughly along the equator.

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Veterinarians in the Washington, DC region have been put on alert for any unusual illnesses in their non-human patients amid today's presidential inauguration—a nod to the significance of potential zoonotic bioterror threats.

In a recent letter to Virginia veterinarians, the state health department requested assistance in the "enhanced surveillance," while noting that, currently, there is no report of threats or bioterrorism-related illnesses.

"As with any large-scale public event, there will be heightened security, and the region will be on alert or signs of bioterrorism or other potential threats," the letter read. "Enhanced surveillance is being conducted out of an abundance of caution."

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When it comes to fine-tuned motor skills like playing the piano, practice, they say, makes perfect. But expert musicians often experience a "ceiling effect," in which their skill level plateaus after extensive training. Passive training using a robotic exoskeleton hand could help pianists overcome that ceiling effect, according to a paper published in the journal Science Robotics.

“I’m a pianist, but I [injured] my hand because of overpracticing,” coauthor Shinichi Furuya of Kabushiki Keisha Sony Computer Science Kenkyujo told New Scientist . “I was suffering from this dilemma, between overpracticing and the prevention of the injury, so then I thought, I have to think about some way to improve my skills without practicing.” Recalling that his former teachers used to place their hands over his to show him how to play more advanced pieces, he wondered if he could achieve the same effect with a robotic hand.

So Furuya et al. used a custom-made exoskeleton robot hand capable of moving individual fingers on the right hand independently, flexing and extending the joints as needed. Per the authors, prior studies with robotic exoskeletons focused on simpler movements, such as assisting in the movement of limbs stabilizing body posture, or helping grasp objects. That sets the custom robotic hand used in these latest experiments apart from those used for haptics in virtual environments.

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