"One part per billion would be akin to a blade of grass on a football field."
I worry about the accuracy of their research if they think there's as many as a billion blades of grass on a football field.
Researchers working on a new type of bomb detector technology have made the rather underwhelming boast that their kit "could soon give bomb-sniffing dogs some serious competition". “Bomb-sniffing dogs are expensive to train, and they can become tired,” said study co-lead author Ren-Min Ma, one of the boffins who came up with …
"I worry about the accuracy of their research if they think there's as many as a billion blades of grass on a football field."
Turns out this is a mathematics project/thing currently used to teach kids how to estimate. There are a number of examples posted online. This one gave the result as "about 63,350,000." A bunch of 5th graders could have told them better.
My favorite example was an angstrom being the amount the water level increased in an Olympic sized swimming pool when a house fly landed on the surface of the water. But similarly that might have been an underestimate and it might be more like the amount an ocean increases being that angstrom is such a tiny measurement.
> where's the published double blind trials, that's what we give the dogs....!
Are there published double blind trials of dogs as drug/explosive/cancer detectors? All the "TV documentary" presentations I've seen appear to have the handler know where the object is and hence open to the "Clever Hans" objection (animal taking cues from handler, not perceiving object).
Whenever I see those cop show sequences of dogs sniffing London Tube passengers' crotches, it makes me think that the only thing stopping a judicial review is the farcical prospect of a barrister asking a police alsatian to explain its training on institutional racism...
They introduced drug sniffer dogs on transit in Vancouver (!!!) after the supreme court ruled that a sniffer dog was reasonable grounds for a search - no SUS in Canada.
The dogs were all Alsatians and when one bit a homeless guy the operators couldn't find any proof that they had received any drug training, then they couldn't find any proof that they had a rabies vaccination. Then they got removed (was only a trial, lessons learned etc etc)
This is what happens when the media starts to believe it's own hype.
Terrorists are not some kind of Bondesque cat-stroking evil supergenuises with seemingly infinite resources at their fingertips. They are fanatics, with an unsystematic knowledge of science and engineering, doing stuff in their basements and kitchens.
But kitchens these days have access to more tools than before. Take vacuum sealers, for instance. Would even a detector as sensitive as claimed be able to pick out explosives double-sealed in vacuum bags, with the inner bag thoroughly washed before being packed in the outer bag? The bags are designed to be gas-tight and diatomic nitrogen and oxygen are smaller than nearly any solid explosive compound I can dredge up.
"get a copy of a terrorist handbook and make it the same way that they do"
Thanks, but no. I'd rather keep my limbs if you don't mind...
If you really like stuff that is not nice to handle (for various reasons), just Google for "Things I won't work with" (for Derek Lowe's blog).
You don't need a big batch of it to test a detector, and could easily keep it below the "blowing your limbs off" threshold.
Though it would seem easier to ask those who work with it if they could part with a quantity equal to a couple grains of sand. However, I suppose there's probably no sanity in the laws governing its control and even that small of a quantity is treated as being just as dangerous as a 55 gallon drum of the stuff.
"...explosives dogs are more or less useless as detectors..."
They seem to do quite well at detecting drugs, and now it seems, even cancer cells. It's interesting they do poorly at explosives. Any particular reason why? Is it poor training, or a "nose" thing that makes them less effective at detecting these particular types of molecules?
As I recall, Drugs dogs do well opposed to bomb dogs because the dogs are actually addicted to the drug(s) they are sniffing for. This is why they have a short working life.
I'm guessing the cancer detection came up as part of Canis Lupis to help them ID the sick prey, and also avoid the possibly dangerous bits.
The bomb-sniffing just doesn't have the evolutionary edge that cancer has, or the motivation of needing their next fix that drug-sniffing has. All it has going for it is the "nose thing".
Or somebody who handles playing cards coated with nitro-cellulose (admittedly a bit rare these days but still extant) or a heart patient with a bottle of "Nitrolingual" (a mixture of ethanol, a few micrograms of nitroglycerine and a soupçon of mint oil) in his or her pocket or any of a dozen other potential false positives.
Looking at the original publication, it isn't competely clear what they are actually detecting. A more sensitive response to ammonium nitrate, a rather involatile salt, than to nitrobenzene, a volatile organic chemical, seems counterintuitive. I'd like to see more experimental detail on how they vaporised the materials and what control experiments they did to rule out other contaminants.
Incidentally, the human nose can detect vanilla at parts per trillion levels.
"Incidentally, the human nose can detect vanilla at parts per trillion levels."
Not everyone. Some can't smell vanilla at all, and there's reason to believe there's a genetic reason for this.
Sensitivity to vanilla IIRC stems from the fact the chemicals responsible for vanilla's odor are also emitted by humans, making it an associative scent.