OK, here's the gossip: (again, I'm not a scientist, but I'm pretty sure nothing here is grossly misleading).

Some background: M22 is the formula used by Alcor, and VM-1 is the solution used by Cryonics Institute. Both are designed by professional cryobiologists, and M22 is patented (as well as being extensively used for cryoprotection of tissues in 'regular' labs).

There's some info here: http://www.evidencebasedcryonics.org/2008/07/08/vitrification-agents-in-cryonics-m22/ VM1 is extremely stable against ice formation at dry ice temps of -80C. However it's more toxic, and wasn't designed for anything other than cooling down. M22 is less stable at -80C, however it's been incredibly cleverly formulated to minimize toxicity, and increase perfusion. It's also got features (such as ice blockers) which come in most handy during the rewarming process, where a lot of damage can occur for cryopreserving organs, etc.

I heard from the designer, Dr Greg Fahy, that he'd run tests holding M22 at -80`C for a week without ice formation, and he gave the impression that too much longer than that might cause trouble.

So as far as long term storage goes, I'd say LN2 is going to be necessary rather than dry ice. However in the future things like Intermediate Temperature Storage (ITS) might make that even more attractive, by preventing fracturing damage.

As a person living in Australia, if I ever died unexpectedly (without having enough time to relocate to Scottsdale), I'd likely be preserved with M22 and sent via dry ice shipping. My take on it is that I'd rather have M22 (Alcor) than VM1 (CI), since good perfusion is so critical in getting a good vitrification in the first place.

Hope this helps!

Yeah, sorry, I felt bad for not acknowledging that bit.

I guess that sufficiently long patient storage at dry ice temperatures would just result in a super thin (nanoscale) layer of ice forming on basically all the nucleation-inducing surfaces (which could then all potentially grow with rewarming), right?

Hmm.. that's a really good question. Off the top of my head I don't know where the actual amount of ice growth over time can be figured out. I'll keep an eye out for more info.

Trouble is, I think, that (depending on perfusion) at -80'C it's water is well below even a suppressed 'freezing point', but still well above the glass transition temp(approx -130'C). So the solution is strongly supercooled and looking for any excuse to shed energy by growing ice crystals, but still mobile enough to rearrange itself to make that happen.

My gut instinct is that it'd be a problem for ice formation on cooling, not just a future rewarming complication, but I'm not sure.

I'm going to go to the Alcor conference next week, if I have the chance I might pose that question to people there. edit: formatting.

Also just another thing that might be interesting:

Check out 'intermediate temperature storage', the idea of storing at a slightly warmer than liquid nitrogen temps (-130'C as opposed to -196'C) is a good idea in order to avoid any fracturing*. This is right near the glass transition temp, so no nucleation can proceed.

Tricky part is there aren't any practical scalable chemicals that have a handy phase change near -130'C, (in the same way that liquid nitrogen does at -196'C) so any system to keep patients there would have to be engineered as a custom electrically controlled device, rather than a simple vat of liquid.

Not impossible, but adds a lot of compexity. They might end up doing it in a few years by putting a dewar in a dewar, and making a robust heater that will failsafe down to LN2 if there's any problem.

*Personally I'm not concerned with fracturing, it seems like a very information-preserving change compared to everything else.

I'm stuck at work for a while, so this is going to be painfully short, sorry.

The bit you're missing is getting below the glass transition temperature prevents both heterogeneous and homogenous nucleation. Dry ice is still well above the glass transition temperature.

Quickest online result I could find for the relevant graph is here: http://www.benbest.com/cryonics/vitrify.html, in section III. Axis labels are "Cryoprotectant concentration" and "Temperature (*C)"

(Although there's a nicer graph Fig3, p36 in Wolker's "Cryopreservation and Freeze Drying Protocols", which just came out this month. Probably not online as of yet)

At very high cryoprotectant concentration (right hand side of the graph) you can transition from 0C to below the Tg without getting in either danger regions (heterogenous nucleation, and homogeneous nucleation). At moderately high cryoprotectant concentration you can transition vertically from 0C to below Tg and only pass through the heterogeneous nucleation danger region, avoiding the homogeneous nucleation region. You typically do this as quickly as posssible, both CI and Alcor have computer controlled systems to accomplish this. With no cryoprotection, or poor perfusion, you pass through the homogeneous nucleation region and ice formation is impossible to prevent.

A typical cryopreservation of a person would have both well and poorly perfused areas, so getting through even the 'safer' danger region of heterogenous nucleation is something you want to do as quickly as possible to prevent ice crystals forming.

/I'm not a doctor, this is just what I've gathered from looking at the research. Hope this helps :-)

Hmm.. wait a tic. Helmets absorb shock if your head hits something. On the motorcycle that's pretty much anything around me. But in the car, what exactly can my head hit?

I drive a recent model vehicle, and there's at least two* airbags around the driver. I can't think of any unprotected objects that my head could strike, that a helmet would help deal with. Plus if I wear a helmet, the added mass my neck supports is going to make it more likely to suffer whiplash, surely?

Not to mention that helmets seem to be designed to stop large accelerations over very short distances (i.e. soft-ish foam a couple of cm thick) whereas airbags are designed to act gently over much longer distances (a pre-perforated membrane that absorbs the blow and deforms over, I'm guessing like 20cm?)

I'm guessing that racing drivers wear helmets because in racing conditions debris is more likely to enter the car, the driver be thrown out of the vehicle, or the car will be deformed/destroyed when struck by another race car at 200km/h. Also the balaclava has a role to mitigating fire/burn risk from fuel spills.

I'm also sign(ing) up for cryonics, and want to make darn sure the lump of tissue between my ears isn't broken, but at the moment I can't see a reason helmets in cars would be a net positive.

*Just checked the web, out of curiosity. I apparently have "Driver and front passenger Advanced Airbag System" and "Driver and front passenger seat-mounted side airbags, driver knee airbag, and front and rear side curtain airbags". So that's 4 airbags that will cover just the driver.

Dang it, days later and I'm still insanely curious to see how the results would differ if the length of the matches wasn't known by the algorithms. Either by removing the concept of limiting matches, or by ending matches far earlier(not just one or two steps) than they were 'planned' to end.

I've been pondering downloading the code, changing and running it, but my shoulder angels start slapping me at the thought of me neglecting my current projects to (even briefly) learn Haskell.

Just occurred to me that there's a way around this, I can offer a shameless bribe to someone else that already knows what they're doing and has some spare time. :-D

With that in mind, $20USD via paypal to the first person who runs the modified tournament and posts the results as a reply to this comment. If you don't want the cash, I'll donate it to MIRI/a charity of your choice, etc.

I'm kinda surprised, my naive intuition was that SimHatingTitForTat would force a cooperative win.

Does anyone know if the lack of SimHatingTitForTat getting into the finals is an artifact of the algorithms knowing the length of the rounds? (I.e. they can decide to backstab on the final turn to get an extra point).

Tongue in cheek thought that just popped into my head: There is no great filter, and we are actually seeing intelligence everywhere because it turns out dark matter is just a really advanced form of computronium.

I have to +1 'Writing essays'.

Too easily overlooked in a technical environment, but it really pays off. Both to assist in consolidating your own ideas, and also in communicating them to others.

Linux/Unix & their associated command line stuff. The number of times it's come in handy to be able to SSH into a machine that's way over there and do stuff is immense. Sadly I waited till Uni to learn, and I wonder where I'd be now if I'd internalised these concepts by the age of 15.

Need to log something you've just done? Redirect the output into a file. Boom. No longer do you have to find the bit of software that does everything, you just need programs that do simple stuff you can repurpose*.

Reading FOLDOC a bit to get the history was handy too. Thinking of computers as CPUs attached to teletypewriters, with all that fancy graphics stuff as optional explains a lot of how current software ended up the way it is.

*Totally not advocating mainstream computing for every user end up like this, btw. (Linux still makes me cry on a regular basis) Just that being able to drop to a command line and chain together commands or write scripts is so powerful that it's a game changer.