20100728

with parasites, you're never alone

It turns out, there are a few viruses with nearly ubiquitous presence in the population that are probably living in your brain right now...

Cytomegalovirus : This one is a favorite. It infects 80% of the population, but usually causes no symptoms. Its known to be latent in a couple types of immune cells, but it may hide elsewhere. Its spread in saliva, so can be transmitted by something as benign as sharing silverware or kissing. As a herpesvirus, it has several tricks for evading the immune system and is a persistent life-long infection. In some individuals, the infection can lead to a syndrome that mimics multiple sclerosis, which (I speculate) may indicate that the virus is replicating in oligodendrocytes, (or just that one antibody against CMV accidentally also recognizes a protein in myelin). This one can also turn lethal in immunosuppressed patients. And, best of all, it probably causes one of the most deadly forms of brain cancer.

Varicella Zoster ( chicken-pox ) : (90%) When I was growing up, it was common for parents to deliberately expose their kids to chicken pox in order to catch this virus in a stage of development where it is least deadly. I kind of hate my parents for this since, if they had just waited, I could of had the vaccine rather than having the lovely little viral DNA in my brain-stem waiting to cause shingles. Fun.

JC virus : 70-90% of the population are carriers. It appears to reproduce primarily using your kidneys, but you'll hardly notice. Its related to BK virus, but that one doesn't eat your brain. SV40 may act similarly. It will eventually come to live in your astrocytes ( support cells in the brain ) and oligodendrocytes ( insulating cells in your brain ). You'll be fine ... unless you get AIDS, have an organ transplant, or need immunosuppression -- then the virus will kill your oligodendrocytes, (killing you). This one spreads readily via sewage (it's shed in urine).

Epstein-Barr virus (Mononucleosis "Mono") : Well known for being spread by kissing, something like 95% of adults in the US have this virus latent in their body. It seems like current research suggests that this herpesvirus lies dormant in B cells, not neurons, but the acute phase of the infection can have neurological complications. It can eventually cause cancers, but I can't find any info on chronic neurological effects at the moment. It might be a cause of some cases of multiple sclerosis.

HSV [1/2]: This is what most of us know simply as "herpes". This one will lie dormant in your brain stem or spinal column, and (might.. might) cause Bell's palsy or contribute to Alzheimer's. If I understand correctly (that is, if I am to believe 7th grade health class and wikipedia), HSV1 is ubiquitous (80%) and you usually pick it up from your parents when you're a kid, while HSV2 is the sexually transmitted variant. So, you probably have HSV1 living in your brain at the moment, and depending on your lifestyle, may or may not have HSV-2 ( apparently often asymptomatic ) there as well.

Honorable mentions :

Measles can remain latent for years in the nervous system, eventually causing Subacute sclerosing panencephalitis, which can kill you over the course of 3 years, with progressive mental deterioration. A similar rare condition can occur with rubella. HIV and prion disease also deserve honorable mentions. Hopefully you know if you have HIV, and prion disease is extremely rare. Polio is still out there and chronic fatigue syndrome might be caused by XMRV. Human T-lymphotropic virus 1 is rare but will cause a chronic neurological disorder. Then, of course, we have the numerous viruses that can cause encephalitis and meningitis. The way Rabies destroys the brain would actually be really cool if it weren't so terrible.

Well, this has been fun, but it turns out that there are even more interesting slow viruses living in some of your other tissues, just waiting to cause a fatal cancer or bring you down should your immune system falter. This makes me wonder how many unexplained diseases may be caused by as yet uncharacterized viruses.

To get a start on some of the other fun and terrifying viruses, see :



20100715

MakerBot : Caveat Emptor

I'd like to discuss my MakerBot. Before I start, I must declare that many people have had success with MakerBot, so this post should be taken only as the real-life facts from the experience of a quite possibly less than competent MakerBot operator. With that out of the way :

New owners of MakerBots may be surprised by the amount of additional time and money required to get full performance out of their MakerBot. While this kit is certainly easier than attempting a full blown rep-rap, it has surprise drawbacks which have left many customers disappointed.

The first thing odd you might notice is that the kind, linear assembly instructions trail off just around the time you think you might want to turn on your MakerBot. Don't panic, it is around this time that you should desperately start bothering the MakerBot google group, since if you proceed blindly you might destroy your bot. MakerBots as they currently ship have a number of design defects, which will require your time and money to correct before you can fully enjoy the printer.

1 : The Teflon™ (PTFE) component of the part that extrudes plastic is prone to melting "losing its structural properties and deforming to an extent that it no longer can serve its intended function". If you've calibrated your temperature sensor incorrectly, or done something odd in assembling the hot end of the extruder, you will quickly destroy your MakerBot by melting deforming this Teflon component. What you weren't told is that this part can be protected by being wrapped in a bit of copper pipe and or hose clamp, but the kit doesn't ship with these. If you destroy this part, you will want to upgrade to an equivalent compoent made of PEEK from MakerGear that is significantly more reliable. Indeed, many MakerBot owners wonder why MakerGear extruder parts are not shipping standard with the kit, since most owners quickly upgrade. I spent about $60 in upgrade parts before I even really got started. I don't actually need all that, but I got some spare pieces in case something else breaks.

2 : You may experience inexplicable behaviors of the printer. Some of these are problems with the engineering on the electronics. Essentially, the electronics are not as noise resistant as they need to be. By default, you will need to twist all cables and install R18 ( 180 ohm ) on the motherboard extruder controller. This resistor does not come with the kit. Many people have also had to install ferrite beads to filter out noise from the lines. These do not come with the kit.

3 : You may find that printing objects with a footprint larger than an inch is very very hard. Why is this ? when the MakerBot advertises a 4"x4"x6" working volume ? As the hot plastic cools, it deforms, and as it deforms, it pulls away from the printing platform. Only very small footprint objects can be printed with the default MakerBot. In order to use the full volume of MakerBot, you will need to purchase the heated build platform (HBP) for $50.

4 : The heated build platform kit is hard to build and incomplete. It requires surface mount soldering. I personally had no trouble with this, but many people who don't breath rosin fumes as part of their metabolism do. Furthermore, the current electronics on MakerBot can not handle the 3-4 amp current the heater draws. You will need to purchase and wire in some sort of relay, solid state or otherwise. Relays don't come from the kit, but a board can be purchased from MakerBot for $15.

5 : Calibrating the software is really, really, hard, and some parts just can't be printed for reasons related more to software than hardware. There is no standard MakerBot calibration file for the 3D printer driver software, but people are working on it. It takes a while to understand this monster and I'm still not done calibrating it for my bot.

6 : The extruder filament feed is under-engineered and hard to make reliable in its present incarnation. MakerBot ships with the MK4 extruder design, but you can buy more functional part from MakerBot for $10, which may or may not solve your troubles, I haven't tried it.

7 : The threaded rods that ship with MakerBot are of sufficiently poor quality that you might find yourself spending days trying to get the Z axis mechanism to work properly. I finally figured out that if I rotated the rods so that they were all bent in the same way, the tension on the driving belt would be closer to constant and my MakerBot would actually work. However, there were many, many days of cursing and manual adjustment, before I arrived at this solution. You can buy new rods at some cost that will be of more correct tolerance. You can also print out parts of a kit ( but not the whole kit ) for correcting "wobble" in your Z axis.

so, to recap :

So, thats totaling at least $100 in upgrades just to get the bot in decent shape ( not including tax and shipping ). Thats not including unexpected repairs, and all the time spent cursing and wondering what you did wrong.

I guess, now that I look at it, $100 isn't that much, but it is evidence that this product is still in the alpha stages of development and cuts several corners, making it failure prone or downright broken. I am confident that with more time spent engineering, and perhaps with a minor $100-$200 increase in the cost of the kit, to increase the quality of the parts, this could actually be workable.

As it stands, many operators have spent hundreds of hours and been plagued with incomprehensible problems, and have never gotten their bots to print a single thing. Other people have had enormous success. I think part of it is down to luck ( how bent are your particular Z axis rods ? ) and pre-existing skill.

So remember, if you buy one of these, it is not a kit for amateur, or even perhaps intermediate hobbyists. If you are a novice at the time you purchase the kit, you will rapidly be required to upgrade your mechanical, electrical, and computer science skill set. It will take some time, and some people still don't have their bots printing. Budget extra time and money. The design cuts corners that can make it hard to work with, and if you buy now you are paying for design refinement that will finally bring the product out of alpha stage. If you do succeed, enjoy printing your calibration cubes. Maybe in a few months you'll work your way up to this.

What I am disappointed about is MakerBot is shipping these kits as if they worked almost right out of the box. They really should be advertising their kits as "parts only, functional MakerBot may require additional parts and design changes". I think that their advertising has been very effective, with many interviews with diverse news outlets. But, I also think that their advertising borders on false or deceptive, and might take some less experienced individuals by surprise.

update : opinions on the MakerBot forum echo these. There is agreement that the kit takes a lot of time and some upgrading may be required, but that this is generally expected for a DIY kit ( I didn't know that ). The argument is that this is still a fair buy for people with lots of time and patience, and that if they start shipping a huge number of kits they might have to put up a notice to adjust expectations closer to reality.

update : After I thoroughly determined that the Z rod defect was beyond my ability to correct, I asked for two new rods from MakerBot. They are shipping the replacement parts at no cost. So, if something really doesn't seem right, and suggestions from the forum aren't helping, and your rational mind determines that the fault is in the part, MakerBot is willing to replace the defect.

update : MakerBot will soon be upgrading their extruder design to Mk5, which should eliminate some of these problems.

So, issues 1,6,7 should be resolved shortly. Issue 2 of electronic noise has been solved on my bot by simply twisting all communications and power wires, and installing the 180 ohm terminating resistor. Issues 3,4 are inherent to the use of ABS : it will warp if not kept warm during the build. I am told that PLA does not suffer from this. Furthermore, issues 3,4 aren't really issues if you're good at soldering and buy all the HBP parts with your kit. Issue 5 isn't going to go away anytime soon since it requires quite a bit of software development. As the kit becomes more standardized and the variance between bots is reduced, a standard calibration may become available.

So I can now update my recommendation for the MakerBot : Research ahead of time, budget a couple hundred extra dollars, budget extra time, be patient, expect to have to improvise hacks, communicate with the forums and if all else fails the MakerBot people themselves. Learn to enjoy the process of building and debugging. If you're technically competent enough, in the end you will probably get a working 3D printer for a very reasonable price, thats easier to assemble and debug than a RepRap.


20100711

I wholly approve of this artwork. If I were in a position to support the arts, I would support this.


uncanny valley ? Whenever we talk about AI in the lab, the assumption always is that the first AIs will resemble people with profound mental retardation or brain damage. That said, having an AI that can pass for a person with mental disability is still a major milestone. I don't think this represents that... I'm hoping that most of these responses are hard coded in a vast dictionary somewhere ( are we certain ours are not ? I know that I hash bits of conversation and store them for later, but I'm weird ).


20100703

Things Vs. Stuff : A Satyrical Philosophy Discussion

Many years ago, Dabney House held a extra super official philosophy discussion on "The Distinction Between Things and Stuff". I recently recalled this discussion, and wondered if the following notions are relevant :


Things are members of finite or countable sets, while stuff is a subset of an uncountable set. I'm not sure what a single element (or other measure-zero subset) of an uncountable set would be... perhaps "nothing".

Confusing theorems like the Banach-Tarski paradox suggest that, if you are working with uncountable sets, notions of volume are poorly defined. This paradox says that if you define a sphere, there is a way to cut up the sphere into parts that can be re-assembled into two spheres. At first glance, this would seem to be an amazing violation of common sense. The reconciliation of this paradox, however, is simply that the human notion of "volume" works poorly on uncountable sets ( and maybe even countably infinite sets). As far as I know, the Banach-Tarski paradox can not be phrased on finite sets of points.

This would imply that "stuff" can not have a definite volume or area, and that some of what we call "stuff" is in fact a very large collection of "things".

Anyway, I'm not an expert or even passably competent in most areas of math, so if F reads this he's probably going to thing "this is dumb, and also wrong, and dumb".

... that is all.