New Paper: Direct Transformation of Vacancy Voids to Stacking Fault Tetrahedra

Direct Transformation of Vacancy Voids to Stacking Fault Tetrahedra

B. P. Uberuaga, R. G. Hoagland, A. F. Voter, and S. M. Valone
Phys. Rev. Lett. 99, 135501 (2007)

Defect accumulation is the principal factor leading to the swelling and embrittlement of materials during irradiation. It is commonly assumed that, once defect clusters nucleate, their structure remains essentially constant while they grow in size. Here, we describe a new mechanism, discovered during accelerated molecular dynamics simulations of vacancy clusters in fcc metals, that involves the direct transformation of a vacancy void to a stacking fault tetrahedron (SFT) through a series of 3D structures. This mechanism is in contrast with the collapse to a 2D Frank loop which then transforms to an SFT. The kinetics of this mechanism are characterized by an extremely large rate prefactor, tens of orders of magnitude larger than is typical of atomic processes in fcc metals.

Selected Stories of Philip K Dick

Warning! Possible spoilers follow (though I will try to keep them to a minimum).

Philip K Dick is one of the more influential science fiction writers, probably ever. His stories have been the inspiration for a number of popular movies, including the Minority Report and Total Recall. They envision a technologically advanced world where what it means to be human is blurred. Many of his stories explore a post-apocolyptic world in which humans are struggling to survive.

The collection Selected Stories of Philip K Dick presents some of his best short stories, including the ones the two movies above were based on. All of his stories cause one to think. Dick lived during the height of the cold war, when the possibility of human self-destruction was at its highest and on the minds of nearly everyone. That, combined with some drug use, led Dick’s imagination to places that are incredible and mind-blowing. Some of his stories are just plain weird. This was epitomized for me by “The Days of Perky Pat”, a story of adults after a nuclear war who spend their times reliving their pre-war lives through the board-game adventures of a doll. The story is just so odd that I could not imagine thinking of such a premise. I mean, some stories, both by Dick and by others, involve a simple premise which the author then explores. The premise isn’t always too radical, it might be something that anyone could dream up. But “Perky Pat” isn’t one of those, at least to me. This story is the product of a mind that just plain sees the world differently.

Not only have Dick’s stories directly inspired mainstream movies, but there are obvious influences his stories have had in a lot of science fiction. The human-looking Cylons of Battlestar Galactica bear an uncanny resemblance to the machines of “Second Variety”, in which a human soldier, at the end, muses that the end of his race might be ok because the robots are already killing one another, already becoming human-like. Some of his stories, such as “Paycheck” (which also inspired a movie), are interesting adventure romps.  All of Dick’s stories, though, convey a unique view of the world, human’s place in it, and the ultimate fate of humanity.

That Dick’s stories provide such an incredible perspective on the human condition begs the question:  how instrumental was his drug use in his ability to devise these stories? It seems to me that many of the great artists, not just authors but painters, musicians, and so on, throughout history used drugs to some extent.  Does this allow a normal human mind to access thoughts and regions of the brain otherwise unaccessible?  Does it allow a person to make connections between otherwise seemingly random ideas to create something new?  If all drug use were completely eliminated, would art suffer?  I personally don’t advocate the use of drugs, but it seems to me that the connections between mind-altering substances and art are pretty strong.

I really enjoyed all of Dick’s stories, even those that start exploring more religious themes.  At least a couple of his stories involve direct interaction between humans and God, with less than predictable results.  But, I was more interested in his commentary on technology and the future of human kind.  I tend not to be a science fiction type of person.  I prefer fantasy.  But, I do enjoy what is termed “cyberpunk” (such as William Gibson and Max Barry) and Dick is a precursor to the cyberpunk genre.   He explores a more immediate future than a Star Wars or Star Trek universe does, though, unlike Gibson and Barry, he does allow aliens in his world.  And the role that aliens play in his world tends to be very disturbing.

I’ll close by saying that a lot of the stories in this collection deal with identity:  what it means to be you, what it means to be human, what separates humans from machines, etc.  These will be important questions as our machines become smarter and smarter and start getting aspects of personality, intelligence and identity.  He also addresses the issues of the individual in society and what role each of us plays in an increasingly technological world.  Again, these questions will become only more important with time.  It thus seems that Dick and his work will continue to reverberate for quite some time.

The Poe Shadow

Matthew Pearl specializes in a somewhat particular sub-genre of fiction, namely historical fiction.  His first book, The Dante Club, was about Longfellow’s translation of Dante’s Inferno to English, which is historical fact.  He adds, though, a series of gruesome murders seemingly based upon the Inferno which Longfellow and his fellow poets must muster up the courage to solve.  It was a very enjoyable book, fast paced and a bit violent.

Pearl’s newest offering is The Poe Shadow.  Again, it is an actual historical fact, the death of Edgar Allan Poe, that is the catalyst for the story.  And the events of the novel, centering on Quentin Clark, are entirely fictional.  Or, are they?  This novel is more than a fictional account of what might have happened to Poe in Baltimore in 1849.  It is Pearl’s hypothesis on what happened, developed after much careful research and the unearthing of new facts connected to Poe’s death.  That he chooses to present his theory in a novel rather than a journal seems to be due more to his desire to use fiction to present his theory than any real weakness in what he has uncovered.

Quentin, a lawyer in Baltimore, is somewhat obsessed with Poe and his writings.  Upon Poe’s death, which is very mysterious, Quentin takes it upon himself, with no small cost to his career and reputation, to uncover what happened to Poe.  This takes him to Paris, where he finds the supposed inspirations for one of Poe’s most famous characters, the detective C. Auguste Dupin.  Much adventure follows as Quentin and the detective return to Baltimore and try to uncover the truth behind Poe’s death before a charlatan beats them to it, or, worse yet, reveals some fictional account of Poe’s death that is believed more than the truth.

There are many subtle twists and turns that occur as Quentin discovers small facts about what happened to Poe during the mysterious 5 days between his first setting foot in Baltimore and his death.  The one unfortunate aspect of the novel, for me, was that the “truth” is revealed at the end of the novel in a very expository way.  The final story behind Poe’s death is related by the detective, Auguste Duponte, in a relatively dry account.  That the hypothesis had to be directly narrated to Quentin, and thus the reader, in this way was somewhat anti-climactic.

However, overall, the book was very interesting and the theory on Poe’s death proposed by Pearl makes good sense, mostly for the fact that it is not sensationalist at all.  All of the mysterious facts surrounding Poe’s death are attributed to relatively minor occurances, each of which, individually, are nothing extraordinary.  It is the accumulation of such details that lead to the mystery surrounding Poe’s demise.

Harry Poutter

So, during our road trip to Oregon, Lisa and I listened to the 5th Harry Potter book on tape, Harry Potter and the Order of the Phoenix. It was the first direct exposure I’ve had to anything Harry Potter. I haven’t read any of the books and I haven’t seen any of the movies. I’ve sort of avoided them. Not so much because I dislike them, but more because I’m not so interested in them either. Because of the mania associated with the product, I’ve just stayed away. But, we had a long drive and it seemed like a good idea to listen to something, and Harry Potter was as good as anything.

First, I must say, I guess I do understand what people see in the Harry Potter world. The story is pretty captivating, though it does seem to dwell on details and side plots that don’t advance the story much. Though, in the end, most of those seemingly tangential story lines do end up coming back into the main narrative and making a difference. And, I did want to listen to the whole story, all the way to the end, which tells you something about how interesting the story was.

I read some reviews on this book on Wikipedia. There were a lot of interesting and odd analyses of the story and the Harry Potter universe in general. There are some saying that since the main characters are all men, the universe is anti-feminist, especially when considering that some loathesome characters, such as Umbridge, are female. Others say that the books are subversive, celebrating youthful rebellion and the bucking of authority.

I didn’t see that much at all. In fact, I took the opposite from the story. Almost everything that happened in Order of the Phoenix was the direct result of Harry bucking authority, but in a bad way. Much of the story concerns his punishment at the hands of Umbridge, but he is punished because he can’t keep his mouth shut. In the end, the climax of the story is the direct result of Harry’s impatience at his situation. He feels like he knows everything and doesn’t trust or believe the adults around him. That is fine, but it is his defiance of those adults that lead to most of the events of the plot, events that often turn out disasterously. If Harry were just a bit more patient and didn’t mouth off and just relaxed, not much would have happened in the story. In short, it seemed to me that the whole story was driven by Harry’s short temper. If he was even keeled, there would have been no story. The story seems to be a lesson against the impetuousness of youth.

Even so, I enjoyed the story. I’m not going to go out of my way to read more, but I won’t avoid the opportunities to see a movie or listen to another chapter of the Harry saga.

Oo la la?

Another reason the summer has been so busy is because of work travel. I just got back last week from a 10 day trip to London and France for a conference on Radiation Effects in Insulators (REI) held in Caen, France. We went to London first to meet with collaborators there who were also going to the REI conference. There were three of us who went from Los Alamos: Kurt, Chris and myself. We stayed in the Kennsington area, very near the Earl’s Court metro stop. After meeting with our London colleagues, the next day we headed south, first to Portsmouth where we caught the ferry to Caen.

The ferry was very nice (on the way out, anyways). It wasn’t too crowded and, while it was a slow mode of transport, it was nice to be able to walk around, get some food and drink (there was a bar on board) and play ping pong. I pretty much sucked at ping pong, but the last game I played, I eeked out a victory (more due to my opponent choking than any real skill on my part). The photo is the sunset from the boat over the water.

The conference was held at the University of Caen, which wasn’t the prettiest thing to look at. It was heavily bombed and essentially destroyed during WWII and had been rebuilt in the 50s or 60s. As such, it had that very functional, boxy look to it. No style to the buildings at all. The cafeteria, though, was very nice. It was very cool to get fresh omelets.

And the conference itself was fine. I gave a talk on the last day, which isn’t the best day to give a talk. I’d much prefer to give a talk early in the week. First, people who might be interested in your work can find you and talk to you about it. And, you don’t have to fret all week about the talk, you just get it out of the way. Then you don’t feel so bad as you enjoy the evenings during the week.

Speaking of enjoying ourselves, the food overall was very good. Not only the cafeteria, but also the local restaurants. One night, we went to a Basque Bistro. While no one there was Basque (except me, perhaps), the food was very good. I had squid in its own ink, another guy had grilled sardines, and everyone was happy. Another night, we went out to the B&B that Kurt was staying at and had a very nice meal. I had a special local menu in which every course was paired with a local cider (the region, Normandy, is known for its ciders). It started off with duck meatballs, went on to pork filets, had an intermediate course of local cheeses, and ended with dessert (which I can’t remember at this moment).

The drink, on the other hand, wasn’t quite as good. I tend to be a beer guy, and France isn’t known for their beer. While I do enjoy cider, and the local cider was good, the beer was just average. The bars had this gimic to make up for it, something they called the “girafe”: a tall column of beer (2.5 liters) with a pour spout at the bottom so you can take the 2.5 liters to your table. Not that it made the beer taste better, but it made it more fun to drink it.

The most notable thing about Caen is the church steeples that fill the city line. And they are all nearly identical, again, a consequence of the bombing: all of the churches were rebuilt after the war. William the Conquerer, who conquered much of Britain from Normandy, is buried in one of the churches, the Men’s Abbey. His wife is buried on the other side of town in the Women’s Abbey. Interesting how the sexes were separated like that.

Caen is very close to the D-Day beaches and, after the conference finished, we spent an afternoon exploring the American Cemetary. It would have been nice to have more time to see the others, but even that much was worth it. Around 9000 Americans died during the Normandy invasion, and you get a sense of that cost in human life by visiting the cemetary. It is amazing to think that almost 3 times as many Americans died during that invasion than have died in Iraq. Maybe that says something about war becoming just a little bit humane (though, that doesn’t consider the cost in Iraqi life). There is a little museum there too, trying to give a sense of how difficult the task of taking those beaches was. Not that I’m in any kind of shape, but just hiking around the hills surrounding the beach winded me slightly. I can’t imagine trying to take the beach and the hills, carrying a bunch of equipment and being shot at.

Afterwards, we took the ferry back, though this time it wasn’t nearly so pleasant. It was full of families with kids, who were screaming their heads off, and parents who were yelling at their kids to stop screaming. But, we survived and made it back to London, where there was a metro strike, so we had to deal with that. The next day, we had some meetings with collaborators at Imperial College. That night, we were all exhausted from the travel, so we just grabbed some dinner at a local pub and called it a night. The next day, we flew home.

The photo is from the airplane as we flew home. I’m always struck with how much of the earth we humans have marked. It seems that there isn’t even a square inch of land we haven’t done something with. From an airplane-eye-view, it is rare to pass over any spot big enough to not have any obvious signs of human activity. I’m both amazed by what we have done and appalled by it as well.

Blah, blah, blah… I've got the blahs.