Later On

A blog written for those whose interests more or less match mine.

Archive for July 2nd, 2015

A strikingly weird—even paradoxical—crystal

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Natalie Wolchover reports in Quanta:

In a deceptively drab black crystal, physicists have stumbled upon a baffling behavior, one that appears to blur the line between the properties of metals, in which electrons flow freely, and those of insulators, in which electrons are effectively stuck in place. The crystal exhibits hallmarks of both simultaneously.

“This is a big shock,” said Suchitra Sebastian, a condensed matter physicist at the University of Cambridge whose findings appeared today in an advance online edition of the journal Science. Insulators and metals are essentially opposites, she said. “But somehow, it’s a material that’s both. It’s contrary to everything that we know.”

The material, a much-studied compound called samarium hexaboride or SmB6, is an insulator at very low temperatures, meaning it resists the flow of electricity. Its resistance implies that electrons (the building blocks of electric currents) cannot move through the crystal more than an atom’s width in any direction. And yet, Sebastian and her collaborators observed electrons traversing orbits millions of atoms in diameter inside the crystal in response to a magnetic field — a mobility that is only expected in materials that conduct electricity. Calling to mind the famous wave-particle duality of quantum mechanics, the new evidence suggests SmB6 might be neither a textbook metal nor an insulator, Sebastian said, but “something more complicated that we don’t know how to imagine.”

“It is just a magnificent paradox,” said Jan Zaanen, a condensed matter theorist at Leiden University in the Netherlands. “On the basis of established wisdoms this cannot possibly happen, and henceforth completely new physics should be at work.”

It is too soon to tell what, if anything, this “new physics” will be good for, but physicists like Victor Galitski, of the University of Maryland, College Park, say it is well worth the effort to find out. “Oftentimes,” he said, “big discoveries are really puzzling things, like superconductivity.” That phenomenon, discovered in 1911, took nearly half a century to understand, and it now generates the world’s most powerful magnets, such as those that accelerate particles through the 17-mile tunnel of the Large Hadron Collider in Switzerland.

Theorists have already begun to venture guesses as to what might be going on inside SmB6. One promising approach models the material as a higher-dimensional black hole. But no theory yet captures the whole story. “I do not think that there is any remotely credible hypothesis proposed at this moment in time,” Zaanen said.

SmB6 has resisted classification since Soviet scientists first studied its properties in the early 1960s, followed by better-known experiments at Bell Labs.

Counting up the electrons in the orbital shells that surround its samarium and boron nuclei indicates that roughly half an electron should be left over, on average, per samarium nucleus (a fraction, because the nuclei have “mixed valence,” or alternating numbers of orbiting electrons). These “conduction electrons” should flow through the material like water flowing through a pipe, and thus, SmB6 should be a metal. “That’s the idea people had back when I started working on this problem as a young guy, around 1975,” said Jim Allen, an experimental physicist at the University of Michigan in Ann Arbor who has studied SmB6 on and off since then.

But while samarium hexaboride does conduct electricity at room temperature, things get strange as it cools.

Continue reading.

Written by LeisureGuy

2 July 2015 at 2:21 pm

Posted in Science

What the TPP will bring

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I am disappointed that President Obama is such an avid supporter of TPP—and of keeping its provisions secret until after it is passed.

TPP-relaced

Written by LeisureGuy

2 July 2015 at 10:55 am

The Real Reason Why Marijuana Is Illegal in the U.S.

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Thor Benson writes at ATTN:

It is hard to imagine a time when most pharmacies carried cannabis and farmers were required to grow hemp, much like they are given incentives to grow corn these days, but that is a significant part of the history of the U.S. From the 1600s to the late 1800s, hemp (a cannabis plant containing very little THC) was harvested on U.S. soil to create materials such as rope, paper, and clothing.

In 1619, the Virginia Assembly decided to require farmers to grow hemp for these purposes, according to PBS. Hemp was also used as legal tender in Virginia, Pennsylvania and Maryland around that time. During the 1800s, cannabis products became a popular medicinal substance found in tinctures that were sold in many pharmacies across the nation. It became a requirement to label these over-the-counter medicines containing cannabis, including cocaine and heroin, with the Federal Food and Drugs Act of 1906, but these things were still legal.

Around 1910, the Mexican Revolution was starting to boil over, and many Mexicans immigrated to the U.S. to escape the conflict. This Mexican population had its own uses for cannabis, and they referred to it as “marihuana.” Not only did they use it for medicinal purposes, but they smoked it recreationally, which was a new concept for white Americans. Even the term, marihuana, was unfamiliar to them, as they called it cannabis.

Southern states that were receiving the Mexican immigrants became concerned with this growing population. Newspapers ran headlines speaking of the “Mexican menace” or the “marijuana menace” and claimed Mexican men were going crazy from smoking marijuana and were killing people. El Paso, Texasbecame the first U.S. city to ban marijuana in 1915, and city officials started rounding up Mexicans who smoked marijuana and had them deported.

“A widow and her four children have been driven insane by eating the Marihuana plant, according to doctors, who say that there is no hope of saving the children’s lives and that the mother will be insane for the rest of her life,” read a New York Times story from 1927. It was clear the newspapers and tabloids were building a campaign against the plant, and much of it has been said to be based on racist ideologies against Mexican immigrants. . .

Continue reading. Videos at the link.

Written by LeisureGuy

2 July 2015 at 10:52 am

Posted in Drug laws

An example of two police officers exonerated by their body-cam videos

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Radley Balko has a good column on a fatal shooting in Texas:

The two disturbing videos below depict the fatal police shooting of James Bushey, 47, of Elkhart, Tex. The videos are taken from the body cameras of two officers with the Palestine, Tex., police department.

Bushey was suspected of stealing some alcohol from a local Wal-Mart. The videos depict Sgt. Gabriel Green calmly and non-aggressively confronting Bushey in the bathroom of an Applebee’s restaurant. He and Officer Kaylynn Griffin then escort him outside the restaurant. Bushey then pulls a BB gun pistol from his pocket and points it at the officers. They then open fire and kill him. By all appearances, this shooting looks both justified and unavoidable. Judging by the local newspaper account of the shooting, Bushey was likely attempting suicide-by-cop. It’s really the only explanation for why he’d knowingly pull a non-lethal gun on two police officers armed with guns that shoot actual bullets.

But these two videos also show why police groups and their supporters ought to embrace the use of body cameras. The most obvious reason is that these particular videos completely vindicate Green and Griffin. Not only do the videos show the shooting to be justified, but they also show that the two officers handled the entire situation professionally and without unnecessary escalation. (Note the moment where Sgt. Green spots a knife on a table and subtly slides it out of Bushey’s reach.) Even if you’re a cynic and believe the officers were only acting that way because they were on camera, that’s all the more reason to embrace the use of body cameras. They can encourage best practices.

Many critics (including me) believe courts and prosecutors are too deferential to police narratives, especially when they’re contradicted by other witnesses. But outside the criminal justice system, any time a cop shoots someone there will always be some suspicion about whether the shooting was justified and necessary. For example, given how inexplicable Bushey’s actions were, it isn’t hard to imagine a critic questioning whether the BB gun was planted. (It wouldn’t be unprecedented.) This is a good example in which an independent video narrative can remove all doubt.

On a broader level, videos like these can also show doubters that there are police shootings that are not only legally justified, but also couldn’t have been prevented. These two videos put you right in the officers’ shoes. It’s hard not to feel the life-and-death rush of adrenaline that undoubtedly washed over Green and Griffin the moment they saw Bushey’s gun.

That perspective is also important. . .

Continue reading.

Written by LeisureGuy

2 July 2015 at 9:54 am

“Look for disconfirming evidence”: Easy to say, difficult to do

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It’s well known that one should also look for disconfirming evidence to test the truth of a statement. In mathematics, looking for a counter-example to any general statement is a reflex. But in real life, we tend to work out a hypothesis and then look for confirming evidence. Somehow we immediately become fans and proponents of our hypotheses and it seems almost rude to try to falsify them: to seek evidence that what we think is true is not, in fact, true at all.

Here’s a nice little interactive test in the NY Times. Try it.

Written by LeisureGuy

2 July 2015 at 7:56 am

Posted in Daily life, Math

Federal Judge: My Drug War Sentences Were ‘Unfair and Disproportionate’

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Conor Friedersdorf reports on a speech by a Federal judge who excoriated the War on Drugs as a failure that has damaged the US severely. He writes:

Former Federal Judge Nancy Gertner was appointed to the federal bench by Bill Clinton in 1994. She presided over trials for 17 years. And Sunday, she stood before a crowd at The Aspen Ideas Festival to denounce most punishments that she imposed.

Among 500 sanctions that she handed down, “80 percent I believe were unfair and disproportionate,” she said. “I left the bench in 2011 to join the Harvard faculty to write about those stories––to write about how it came to pass that I was obliged to sentence people to terms that, frankly, made no sense under any philosophy.”

No theory of retribution or social change could justify them, she said. And that dispiriting conclusion inspired the radical idea that she presented: a call for the U.S. to mimic its decision after World War II to look to the future and rebuild rather than trying to punish or seek retribution. As she sees it, the War on Drugs ought to end in that same spirit. “Although we were not remotely the victors of that war, we need a big idea in order to deal with those who were its victims,” she said, calling for something like a Marshall Plan.

She went on to savage the War on Drugs at greater length.

“This is a war that I saw destroy lives,” she said. “It eliminated a generation of African American men, covered our racism in ostensibly neutral guidelines and mandatory minimums… and created an intergenerational problem––although I wasn’t on the bench long enough to see this, we know that the sons and daughters of the people we sentenced are in trouble, and are in trouble with the criminal justice system.”

She added that . . .

Continue reading. At the link, a video of the talk.

Written by LeisureGuy

2 July 2015 at 7:40 am

Smooth shaving with Feather Pro Super

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SOTD 2 July 2015

A very nice shave indeed. The Rooney Style 2 Super Silvertip is now totally reliable, and it made a really fine (and fragrant) lather from Dr. Jon’s Anne Bonny: West Indies Bay, Black Tea, Dark Rum, and Lime. I’m shaking the brush a bit too much, I note: I had to add a good driblet of water and work it into the lather on my beard, but that’s easily done and extends the lathering a bit, giving the lather more time to accomplish its mission.

This is the satin-finish Mongoose, and I loaded a new Feather Pro Super blade. It occurred to me that I could alternate this with the Kamisori blade in the polished Mongoose and get a better/faster comparison. In this shave, the Feather Pro Super does seem to be a bit sharper—i.e., shaving slightly more easily. I got one really tiny nick in the middle of my upper lip, but My Nik Is Sealed took care of that.

A good squirt of the highly fragrant and very pleasant Frozen Cranberry Aftershave Balm, a Father’s Day gift from Soap Smooth of a limited edition. Very nice finish.

Written by LeisureGuy

2 July 2015 at 7:24 am

Posted in Shaving

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