An Ignoble Experiment: The 7: High stakes in New Hampshire’s primaries; an unusual Alzheimer’s symptom; prehistoric super-shark; and more

Good morning. It's Tuesday, Jan. 23, and I probably won't be rushing to try Reese Witherspoon's controversial snow recipe. Now let's catch up.

The stakes: A decisive win for Donald Trump could sew up the Republican nomination and force his last challenger, Nikki Haley, to consider the future of her campaign.
What to expect: The last polls close at 8 p.m. Eastern. Results should start trickling in soon after, though s ome votes have already been counted.
A different day for Democrats: President Biden won't appear on the ballot because of party rules. Voters are being asked to write his name in, which could delay results.

What happened? The soldiers were rigging buildings with mines when a grenade hit a nearby tank, triggering the mines and collapsing the buildings with the troops inside, Israel said.
The bigger picture: This was the deadliest single incident for the country's military in the Gaza Strip since it began its operation there in October.

The ruling: U.S. Border Patrol agents can get rid of razor wire Texas officials installed along part of the border while legal challenges continue, the court ordered yesterday.
Zooming out: This is one of several legal battles between Texas Gov. Greg Abbott (R) and the Biden administration over immigration, border security and the state's aggressive actions.

What's happening? Fulton County District Attorney Fani Willis is accused of having an inappropriate relationship with the lead prosecutor in the election interference case.
Why it matters: The allegations, which Willis hasn't commented on, have led to calls for her removal and may have damaged the case against the former president and 14 others.
The latest: A judge unsealed the prosecutor's divorce file yesterday.

What happened? Two to 3 inches of rain fell in three hours. It was the wettest January day in the city's history, and it caused widespread dangerous flooding in urban areas.
Another wild weather phenomenon: More than a dozen wintry whirlwinds dropped nearly 3 feet of snow around Lake Michigan on Friday, stunning meteorologists.

What to know: This variant of the disease begins with vision problems rather than memory issues. It starts affecting patients at age 59 on average, a new study found.
Why it matters: Around 700,000 Americans could have this condition. But the unusual early symptoms mean that many go years before getting the correct diagnosis.

What is it? The megalodon, which lived 3.6 million years ago. We know it had teeth as big as human hands, but there's disagreement over exactly what it looked like.
What's new? It may have measured over 50 feet from nose to tail, and it was more slender than movies like "The Meg" have suggested, a recent study said.