Recently I learned that horseshoe crab blood is blue, not red, due to their use of hemocyanin in place of hemoglobin to transport oxygen (copper vs iron). It turns out I should have investigated further, because their blood is more than just different, it's actually useful.

Their blood also contains amebocytes, which are similar in function to white blood cells, but differ in their response to pathogens: in the presence of endotoxin, the blood clots vigorously. Endotoxin is a toxic bacterial component that sticks around after all the pathogens in a solution have been sterilized. It causes a fever, and it's pretty hard to detect. Rabbits were injected to test batches of drugs, since they react to endotoxin similarly to humans, and if they got sick, that lot was rejected.

But horseshoe crab blood can help, and we don't have to get them sick as part of testing! The link I got most of my information from starts reading like a brochure at this point, but the gist is that every year a whole lot of horseshoe crabs get collected, 30% of their blood is drawn, and they're returned to the wild, and they are generally not harmed in any way unless collection goes badly. Back in the water, blood volume rebounds in about a week, and cell count returns back to normal in about 3 months.

The blood isn't used as-is in the lab these days, it's processed into limulus amebocyte lysate, reconstituted with water, part is tested against control samples, and the rest used to test injectable drugs and related medical things that you don't want getting you sick.

Variable Geometry Turbocharger

By changing the geometry of the turbine inlet, a turbo's effective range can be extended to the lower and upper ends of the engine's range, while eliminating the need for a wastegate.

Taking the adjustment capability a step further, the geometry can also be changed to purposefully increase exhaust backpressure to promote exhaust gas recirculation, reduce emissions, provide additional engine braking, and increase exhaust temperature for the purpose of regenerating a diesel particulate filter. While increased exhaust backpressure does not increase the efficiency or power of the engine, it can still be used beneficially during short periods (like when shifting).

The diesel particulate filter is also interesting: it captures microparticles and soot and regenerates (or cleans) itself via the application of high heat for a short period to burn away the particles. It can be functionally compared to the catalytic converter of a petrol-powered car (they can share the same structural materials) but instead of requiring oxygen to recharge the catalyst, it uses heat to clear the filter.

when Milami got photorefractive keratectomy on Thursday, they let me into the operating room with my camera gear.

Milami went in for photorefractive keratectomy today and I got to watch the operation armed with my still camera.

the robocam used for targeting by the eye laser software also records the whole thing to DVD, here for your pleasure.

thanks to DJCapelis for sending me this link to an article from 1960 on hobbyist X-ray machines titled An Inexpensive X-ray Machine. it always delights me to read about historical hacks and how they were developed.

a sample from the article: