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99 comments

For example (0, Funny)

Anonymous Coward | more than 7 years ago | (#17746130)

I heard on the radio today that dynamite looked like red sticks.

BAM! I am NOT a Google SHILL !! Is that CLEAR NOW (-1, Troll)

Anonymous Coward | more than 7 years ago | (#17746618)



BAM! I am NOT a Google SHILL !! Got it !!

Ha. (0)

badenglishihave (944178) | more than 7 years ago | (#17746152)

Like I'm going to let airport security subject my laptop to "nitrogen nuclear quadrapole resonance". Sounds like an electronic death wish to me ;) .

Re:Ha. (1)

mr_mischief (456295) | more than 7 years ago | (#17751644)

X-rays are much safer for your laptop than the giant magnet they use to detect metal on you.

Re:Ha. (1)

sciguy123 (1056876) | more than 7 years ago | (#17793602)

I agree that x-rays of the energy and intesity used in aviation security application will have no adverse effect on laptops, but neither will metal detectors. The "giant magnets" you speak of exist only in your imagination. Metal detectors us low power rf continuous or pulsed waves. They pose no danger to people unless they have a very poorly designed implantable medical device (pacemaker, neural stimulator, insulin pump, etc). All of these devices designed in the past 15 years are unaffected.

White powders? (2, Insightful)

Some_Llama (763766) | more than 7 years ago | (#17746168)

SO will it detect Cocaine, herion, anthrax, flour? What if I add some gun powder to my Coke?

Re:White powders? (5, Funny)

Anonymous Coward | more than 7 years ago | (#17746586)

"What if I add some gun powder to my Coke?"

Then I hope you're snorting it, not smoking it.

Re:White powders? (1)

dgatwood (11270) | more than 7 years ago | (#17748346)

"What if I add some gun powder to my Coke?"

Then I hope you're snorting it, not smoking it.

I'm drinking it, you insensitive clod!

Interesting idea, but one caveat I perceve... (1, Interesting)

MBC1977 (978793) | more than 7 years ago | (#17746170)

Hmmm.... seems plausable, since if my memory serves me correctly, all matter gives off a distinct waveform. Just one question (or problem?), what happens if the crazy terrorist (er.. freedom fighter) decides to make a trigger which works off of radio waves (or whatever particular radio wave) said name future machine may use?

Re:Interesting idea, but one caveat I perceve... (5, Insightful)

Dr. Eggman (932300) | more than 7 years ago | (#17746218)

What if a crazy man just straps some bombs on, walks up to the security checkpoint and sets himself off? There's no security check to protect the first security check. Better add one.

...and recurse.

Re:Interesting idea, but one caveat I perceve... (0)

Anonymous Coward | more than 7 years ago | (#17746970)

Or just make the sensors able to detect bombs approaching them from a distance. This can alert the security forces and possibly even an approach direction, distance and speed to look out for.

Re:Interesting idea, but one caveat I perceve... (1)

f_raze13 (982309) | more than 7 years ago | (#17747926)

You misinterpret what he was asking. If the bomb was set to detonate when it recieved the radio waves from the detector, it wouldn't matter from how far away the bomb was detected, it would still explode, causing massive casualties.

Re:Interesting idea, but one caveat I perceve... (1)

yerM)M (720808) | more than 7 years ago | (#17750284)

Having recently travelled extensively around the world, many foreign airports have checkpoints as you enter the airport. It seems stupid that our major airports do not do this. I can guarantee that there are far fewer people at the checkpoint than standing at line at the ticket counter.

Re:Interesting idea, but one caveat I perceve... (1)

mpe (36238) | more than 7 years ago | (#17751964)

What if a crazy man just straps some bombs on, walks up to the security checkpoint and sets himself off? There's no security check to protect the first security check. Better add one.

What you'd need would be explosive detectors at the main doors to the airport. But also at train stations, sports stadiums, etc. There is no reason to assume that suicide bombers (or the people who pick their targets) are obsessed with air travel.
You also need a low rate of false positives. As well as being able to deal with the situation of a bomb carrier who does not realise they are carrying a bomb. e.g. "Deliver this package for me and I'll pay you when you come back".

Re:Interesting idea, but one caveat I perceve... (2, Insightful)

CosmeticLobotamy (155360) | more than 7 years ago | (#17746222)

what happens if the crazy terrorist (er.. freedom fighter) decides to make a trigger which works off of radio waves (or whatever particular radio wave) said name future machine may use?

Given the availability of both clocks and button, it seems unlikely to come up often.

Re:Interesting idea, but one caveat I perceve... (0)

Anonymous Coward | more than 7 years ago | (#17746226)

they can already blow up the baggage scan machines if they wanted (x-ray detector, timer, etc), but they want the bombs on the plane- which means if it goes off from RF, they don't make their goal.

Re:Interesting idea, but one caveat I perceve... (1)

Goaway (82658) | more than 7 years ago | (#17746346)

Pretty much the same thing that happens if a terrorist walks up to the check-in and presses the trigger in his pocket. Why do you ask?

Re:Interesting idea, but one caveat I perceve... (0)

Anonymous Coward | more than 7 years ago | (#17746392)

Just one question (or problem?), what happens if the crazy terrorist (er.. freedom fighter) decides to make a trigger which works off of radio waves (or whatever particular radio wave) said name future machine may use?

Umm... Ohh... Uhhhh... Oh, I know! An EXPLOSION!

Re:Interesting idea, but one caveat I perceve... (1)

Nethemas the Great (909900) | more than 7 years ago | (#17756932)

Hmm... And how many billions would it take to roll this toy out everywhere and would it detect the guy carrying something fun in his briefcase before he detonates it while in the security check line? Any how many billions would it take to just simply treat the third-world with some dignity and respect?

--Neth

So, no more taking shoes off? (2)

mi (197448) | more than 7 years ago | (#17746178)

Cool! When can the new technology allow us to walk through the security with dignity again?

Re:So, no more taking shoes off? (5, Interesting)

QuantumG (50515) | more than 7 years ago | (#17746414)

Please take off your: jacket, shoes, backpack (and take the laptop out of the backpack and put it in a seperate tray), hat, belt, mobile phone, keys, wallet (if it contains more than 3 rfid based entry keycards). Yes, I travelled international recently. It's not even consistent.. some places they'll make you take off your belt, other places, no, that's fine.

Time before last I took a suit coat with me. Big solid metal coat hanger with nice sharp edges. They just let me carry it onto the plane. Had I tried to take a similar piece of metal on (say, a boxcutter) they would have denied me. Hmmm, wonder if there's a little big of class disparity there.

The illusion of safety.

Re:So, no more taking shoes off? (3, Insightful)

bram (490) | more than 7 years ago | (#17747422)

Last time I took Sri Lankan from EU to CMB. I'm not allowed to have my swiss army knife in the cabin so I put it in my cargo luggage.
When we got our meal it came with nice metal cutlery.

On arrival I put the metal meal knife in my hand luggage and walk out of the airport.
One month later I go back to EU wondering what security would tell me checking in with one of their own knifes.

Nobody saw anything, now it's laying somewhere here around the house.

So much for regulations and security.

Re:So, no more taking shoes off? (1)

The_Dougster (308194) | more than 7 years ago | (#17748964)

That is such crap. If I am expected to surrender my concealed weapons, then I think that I should expect an armed escort by military personnel.

The current airport *security* plan is a joke. I have never felt more threatened in my life except when I have been in airports. They should issue all citizens complimentary handguns, then I'd feel a bit safer, and if there was a shootout, we'd have the numbers on our side at least.

Re:So, no more taking shoes off? (1)

bozendoka (739643) | more than 7 years ago | (#17747542)

Hell, I made it on a plane to Canada with a 2" keychain knife. Not so much luck on the way back.

Re:So, no more taking shoes off? (2, Funny)

ari_j (90255) | more than 7 years ago | (#17748112)

Two things:
1. I have just started stripping down to my underwear every time I fly. There's no sense having to be asked to take off any article of clothing, so just take 'em all off and throw them in the tray. It saves everyone time and embarrassment.
2. Why not use a real man's portable hanger [indyprops.com]?

Re:So, no more taking shoes off? (1)

MountainLogic (92466) | more than 7 years ago | (#17754158)

Just be very glad that Richard Reed tried to blow up his shoes and not his underwear

Re:So, no more taking shoes off? (1)

ari_j (90255) | more than 7 years ago | (#17757822)

I'm still waiting for the breast implant bomber. Once someone tries that, I'm going to sign up for a security job immediately.

Re:So, no more taking shoes off? (0)

Anonymous Coward | more than 7 years ago | (#17748208)

I know what you mean. I recently went Amsterdam Schipol to Houston Intercontinental, at the checkpoint in Amsterdam they made me take off my shoes and belt, but I was allowed my cigarette lighter. Go figure.

Re:So, no more taking shoes off? (1)

dyslexicbunny (940925) | more than 7 years ago | (#17747312)

TSA Memorandum

We will be integrating a new explosives detection device to all screening areas which uses radio waves in some crazy science fashion. Unfortunately, the radio waves can't pierce the human body and provide accurate results. Therefore, all domestic and international flights are required for a pre-security cavity search. Passengers concerned about mantaining dignity must be additionally screened as they may be supporting terrorism.

That is all.

Re:So, no more taking shoes off? (1)

Builder (103701) | more than 7 years ago | (#17749026)

You can walk through your airport with dignity again just as soon as all the sheeple realise who actually owns a democracy. As soon as the people decide this is too much, it will be over.

This means that it will never be over :(

Awsome! (0)

Anonymous Coward | more than 7 years ago | (#17746246)

Radio waves! So, they'll send a signal out that'll trigger the bombs those assholes made, blowing those assholes up while they're still in their caves?

Detecting explosives via radio waves (1)

kcbrown (7426) | more than 7 years ago | (#17746262)

That's easy!

All you have to do is go through all the frequencies being used by the radio triggers and send a "detonate" signal on each such frequency.

I guarantee you'll detect the explosive when it goes off...

Hey, it's better than having it go off on the plane, right? :-)

Re:Detecting explosives via radio waves (1)

Alchemist253 (992849) | more than 7 years ago | (#17749434)

A similar approach has been used in Iraq to detonate roadside bombs in advance of convoy movement. A commander discovered that the detonators transmitted the same frequency as RC car controllers. He thus taped down the controls on such a controller and - voila - IEDs would detonate a safe distance in front of his convoy.

Never underestimate the utility of relatively low-tech solutions.

Re:Detecting explosives via radio waves (0)

Anonymous Coward | more than 7 years ago | (#17755980)

Nor should we underestimate the ingenuity of our guys and gals in the field. Regardless of whether you're for or against the war, make sure to give thanks to the people fighting over there, figuring out ways to keep not only themselves and their fellow troops alive, but also the civilians and otherwise who might have gotten killed as well.

Explosives and radio waves... (2, Insightful)

Roskolnikov (68772) | more than 7 years ago | (#17746280)

I remember hearing warnings about having transmitters near my explosives, something about accidentally triggering professional grade gear;
Exposing high strength radio waves to homemade devices might result in detection by detonation.......

It's not a cure-all (1)

hypermanng (155858) | more than 7 years ago | (#17746300)

Nothing (plausible) can detect everything that might be explosive, but it would seem this targets the most easily-obtained explosives and should raise the bar significantly in terms of the technical competence it takes to defeat the security measures.

That said, it would seem to have a ways to go before it's practical.

Re:It's not a cure-all (2, Interesting)

budgenator (254554) | more than 7 years ago | (#17746660)

Nothing (plausible) can detect everything that might be explosive, Actually even what an explosive is can be kind of ambiguous; still I've read that terrorists are more likely to use peroxide based explosives rather than nitrate based explosives. I see the nitrogen nuclear quadrupole resonance as have more potential in finding IED in the road beds in places like Iraq.

Re:It's not a cure-all (2, Interesting)

Entrope (68843) | more than 7 years ago | (#17746866)

NQR detectors tend to be relatively slow to examine an area, and a very important factor in Iraq is a fast rate of advance. NQR might work for airports, but other systems -- like metal detectors and backscatter radars -- work better when you need to go fast. The military mostly looks at NQR as a confirmation technology for other detectors and not as the first line of explosive threat detection. (Google "NQR rate of advance" for various papers and studies on the issue.)

Re:It's not a cure-all (1)

jstott (212041) | more than 7 years ago | (#17761776)

The military mostly looks at NQR as a confirmation technology for other detectors and not as the first line of explosive threat detection.

It's also being looked at for landmine detection (I did some work on a competing technology for a time once). NQR has better sensitivity than the WWII-vintage metal-detectors at a comparable rate of forward advance. Also, most mines have very little metal any more, mostly because using plastic is cheaper. That plastic also makes it harder for a metal detector to find them is just a side-benefit.

-JS

Re:It's not a cure-all (2, Informative)

calidoscope (312571) | more than 7 years ago | (#17748042)

I see the nitrogen nuclear quadrupole resonance as have more potential in finding IED in the road beds in places like Iraq.


Snicker....


As was pointed out by 'Entrope', NQR is probably not the best choice for detecting roadside IED's - there are other methods better suited for rapid scanning. What NQR would be good for is confirming whether or not a non-conducting anomaly picked up ground penetrating radar contains explosives.


You are correct in stating that NQR would be ineffective against peroxide explosives. The explosives that NQR is especially effective at detecting are also the ones with essentially zero vapor pressure that give problems for trace detectors.

Even more effective: (1)

Penguinisto (415985) | more than 7 years ago | (#17746320)

up the wattage a bit and you'll stop all explosives from ever getting onboard.

...course, it might be a bit hazardous to bystanders and make a mess, but if they're really serious...

/P

If they were really serious (1)

geekoid (135745) | more than 7 years ago | (#17746402)

that would make everyione undress, give them on orange jump suit and send all there things in a cargo plane to meet them.

Possible medicate them into a stupor.

Re:If they were really serious (1)

Atlantis-Rising (857278) | more than 7 years ago | (#17746588)

Don't give them ideas. Air travel's bad enough as it is. If you absolutely must fly, don't fly out of international airports- fly out of local trans-border/civil aviation ones, where security is much more lax.

Re:If they were really serious (1)

rlp (11898) | more than 7 years ago | (#17748150)

> would make everyone undress, give them an orange jump suit and send
> all their things on a cargo plane to meet them.

Yeah, I've flown that airline.

> Possibly medicate them into a stupor.

Only, if you get the upgrade to first class.

All that security is for... (2, Insightful)

JCOTTON (775912) | more than 7 years ago | (#17747554)

guarding the planes. To hell with the people on the ground. Why do you think that security is set up in the MIDDLE of the airport? What if a bad guy wanted to kill people in the terminal? Wide open. That is why in Israel, the security is at the front gate., not the flight gate.

That's nice (4, Insightful)

overshoot (39700) | more than 7 years ago | (#17746332)

I wonder how it is at distinguishing between common metallic solids and thermite?

A little oxidized iron, a little aluminum powder, a tiny amount of binder, press, and you have the makings of some attractive plaques or statuary. A bit of magnesium wire and a battery and you have everything you need to start a large mass of aluminum burning. Spectacularly.

Good thing none of the Bad Guys have the brains of a flatworm. Or at least, that's what our whole air travel security strategy assumes.

Re:That's nice (1)

Kozz (7764) | more than 7 years ago | (#17747010)

Okay, well, thermite is some really fun stuff, but it's hardly an explosive. Damned hot molten iron, to be sure, but it's not going to go "ka-boom". Or do you know something I don't?

Re:That's nice (1)

overshoot (39700) | more than 7 years ago | (#17747064)

Damned hot molten iron, to be sure, but it's not going to go "ka-boom". Or do you know something I don't?
Yeah. Airplanes are made of aluminum and have a 600 kph forced air feed.

Re:That's nice (1)

RobertLTux (260313) | more than 7 years ago | (#17747304)

hows about this you setup your rig it gets put in the cargo hold and then at 30K it goes off and turns into a glob of metal

possibles
1 fire on the plane torch the luggage (fail the airframe)
2 very large hole in the plane (the cargo hold drops to not many psi or 0.0?? atmospheres)
3 get very lucky and you might sever the flyby wire system (oops backups should get the plane on the ground)
4 depending on what the plane is doing you might hit a fuel tank (fails the airframe OOH NIFTY KABOOM)

Thermite in luggage probably won't work (3, Insightful)

Harmonious Botch (921977) | more than 7 years ago | (#17747970)

Luggage probably does not burn very well. The suitcase and its contents are mostly fabric / leather / plastic of some type. ( think about what you packed last time... ) Most clothing has passed some kind of won't-sustain-combustion test, and that in the presence of lots of oxygen at or near sea level. Leather won't sustain a fire on its own. Plastics, who knows? But few are highly exothermic.
And add to that the fact that there is not a whole lot of air available in the luggage container - it's mostly luggage. Even if there is enough fuel to sustain a low-temp fire, it soon suffocates itself. The only jet that has crashed in the last few decades due to a cargo fire was because there was an oxygen tank in the luggage.

Also, according to federal law, all luggage compartments on commercial airliners are required to have fire-resistant walls.

Re:Thermite in luggage probably won't work (1)

P3NIS_CLEAVER (860022) | more than 7 years ago | (#17751958)

I hate to break it to you but thermite does not need oxygen to burn.. It will just melt through the suitcases and then the fuselage....

Re:Thermite in luggage probably won't work (1)

Harmonious Botch (921977) | more than 7 years ago | (#17754594)

I agree, it does not need 02. Thermite has it's own oxygen bound up in Fe203. I never assumed otherwise.
Of my ten-sentence post, nine sentences are devoted to the question of whether or not luggage will burn.
The tenth sentence notes that when the thermite does finally get thru the luggage ( if the terrorist is lucky enough to have his suitcase on the bottom layer ) it will hit the fire-resistant wall/floor of the container.

Please RTFP.

Re:That's nice (1)

overshoot (39700) | more than 7 years ago | (#17750870)

hows about this you setup your rig it gets put in the cargo hold and then at 30K it goes off and turns into a glob of metal

possibles
1 fire on the plane torch the luggage (fail the airframe)
2 very large hole in the plane (the cargo hold drops to not many psi or 0.0?? atmospheres)
3 get very lucky and you might sever the flyby wire system (oops backups should get the plane on the ground)
4 depending on what the plane is doing you might hit a fuel tank (fails the airframe OOH NIFTY KABOOM)

Never been much around thermite, have you?

The stuff turns into a blob of iron and alumina at thousands of degrees Celsius, which will "drip" through an amazing amount of just about anything on its way to the center of the Earth.

A kilogram of it won't have any problem at all getting to the skin of the bird -- which it will immediately heat to well above the ignition point of aluminum. If you have enough of it (and I don't know what "enough" is but am willing to bet it would fit in a suitcase) you can get that skin to a sustainable reaction, especially given the above-mentioned forced air feed.

Have you ever seen an aluminum fire? Now consider a hundred tons of aluminum fire ...

Re:That's nice (1)

mpe (36238) | more than 7 years ago | (#17751856)

hows about this you setup your rig it gets put in the cargo hold and then at 30K it goes off and turns into a glob of metal

Thermite creates moltern iron. Which will follow the force of gravity until it encounters something strong (and heat resistant enough) to stop it.

1 fire on the plane torch the luggage (fail the airframe)

Even if the luggage is entirely flame retardant it's unlikely to do much to stop the molten iron.

2 very large hole in the plane (the cargo hold drops to not many psi or 0.0?? atmospheres)

The cargo hold has the same pressurisation as the cabin. Which measured as an altitude of 8,000 feet.

4 depending on what the plane is doing you might hit a fuel tank (fails the airframe OOH NIFTY KABOOM)

The only thing in any fuel tank which can explode is the fuel vapour/air mixture in the top of the tank. Then only if the fuel vapour and air are mixed in the right ratio. Airliner fuel tanks are unpressurised and vented. About the only chance of a fuel/air explosion would be from termite placed in the cabin above the centre wing tank. The complication is that a soon as the molten iron entered the tank it would be followed by higher preassure air from the cabin. Thus you'd need an explosive mixture to exist before the iron fell into the liquid fuel.

Re:That's nice (0)

Anonymous Coward | more than 7 years ago | (#17749866)

This thing detects nitrogen (as in nitroglycerin, TNT, almost about everything that goes boom).

Almost.

Guess I'll just have to whip up some permanganate then! No nitrogen there. Or a chlorate.. or pick your oxidizer, connect it to something that burns really well.

(Or for bonus points: carry a sulfate. Electrolyze sulfuric acid and generate nitrogen oxides by arcing. Then you probably know what to do with the nitric acid, but people may get really suspicious of WTF you are doing.)

Re:That's nice (1)

mpe (36238) | more than 7 years ago | (#17751278)

Okay, well, thermite is some really fun stuff, but it's hardly an explosive. Damned hot molten iron, to be sure, but it's not going to go "ka-boom". Or do you know something I don't?

Melting through the skin of an airliner in flight is quite likely to cause an explosive decompression. Possibly more dangerous if set off above the cargo areas than the Centre Wing Tank.

nuclear resonance is MRI without the "imaging" (5, Informative)

kris_lang (466170) | more than 7 years ago | (#17746340)

so this is called nuclear magnetic resonance spectroscopy.

Doing it with a gradient field and a special pulse sequence lets you get the
vibrational amplitudes of your protons based on their position within the gradient field.
That's what gets you MRI images. Before MRI images, nuclear spectroscopy was used to
resonate the "nucleus" of atoms/molecules/conglomerations of molecules at varying radio-frequencies to see if there was any resulting resonance and output RF (radiofrequency) signal.

Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it.

MOD PARENT TROLL (0)

Anonymous Coward | more than 7 years ago | (#17746464)

The above is so wrong that I don't know where to start.

Re:nuclear resonance is MRI without the "imaging" (5, Informative)

Anonymous Coward | more than 7 years ago | (#17746476)

... but this is NQR which is examing the 4th order (as I can recall, maybe is was 2nd-order, I don't remember anymore:-p) of the nucleus. It's very similar underlying principles as MRI and NMR (and thus implementatin scheme is similar) but the physical interaction mechanism is the quadrapole momeent rather than the dipole moment of the nucleus.

The problem with NQR and SQUID is that the measurement is extremely sensitive and it is difficult to filter out false positives. SQUIDs are very sensitive to magnetic perturbations and noise. Heck in the lab it can pick up the noise caused by the underground train. So the design has to be extremely precise and the filters need to be carefully designed. Also NQR technique only can detect certain substances that contain the molecular signature of interest (in this case N14 (i think?)). You need to induce a very large magnetic field (relative to the nucleus) to induce NQR. The SQUID can pick up the magnetic distrubance, but you still need to induce the field. DARPA showed some demos of remote systems that could acheive this. The problem was the false positives were pretty high, because it turns out shoe soles haave N14 which can trigger a false positive.

Nevertheless, it's a great acheivement and I hope they can iron out the kinks in this technology.

So don't put those shoes in your baggage! :-)

Re:nuclear resonance is MRI without the "imaging" (0)

Anonymous Coward | more than 7 years ago | (#17746628)

Thanks for the info.

That actually taught me something.

Wish I had mod points tongiht.

I think the magnet is the Achilles heel (1)

Quadraginta (902985) | more than 7 years ago | (#17748902)

You need to induce a very large magnetic field (relative to the nucleus) to induce NQR

I'd say there's the rub. I'm sure everyone here has seen the enormous magnets used in nuclear magnetic imaging, if only on the television. And at that an MRI patient has to sit still for half an hour. You can't take half an hour to scan a bag, you've got to do it in a second or two. So that means you need a truly huge, multimillion-dollar magnet, to collect your signal fast enough.

Sheesh. Much cheaper to just put a bin of loaded .38s next to the boarding gate, for any interested adult to bring on board, just in case. (Another bin near the exit gate collects the unwanted weight afterward.)

Re:nuclear resonance is MRI without the "imaging" (1)

sciguy123 (1056876) | more than 7 years ago | (#17793654)

not all n14 is equal. NQR frequencies and pulse patterns are specific the the quadrupolar crystaline structure that the nitrogen is bound in. Thus ALL n14 containing substances discovered so far that exibite NQR signals have distinct "fingerprints'. N14 in shoe leather is a non-issue. That said, NQR does have many limitations that make it best for a complimentary technology and not a magic bullet.

Re:nuclear resonance is MRI without the "imaging" (0)

Anonymous Coward | more than 7 years ago | (#17746808)


Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it.

Score: -1,Horseshit

Re:nuclear resonance is MRI without the "imaging" (2, Informative)

candover (39486) | more than 7 years ago | (#17747054)

Protons resonate at 2.4 GHz approximately

No they don't. Nuclear magnetic resonance requires a strong external magnetic field. The strongest superconducting magnet you can buy today induces a resonance (the Larmor frequency [gsu.edu]) in protons at 950 MHz... but it costs about ten million dollars and only does that over a tube about five centimeters wide. The absolute strongest MRI magnets today top out at about 1/3 of that magnetic field, and most are far less.

Microwaves heat food via RF heating [wikipedia.org], which is an electric effect, not a magnetic one. No relationship to the mechanism of NMR at all.

As for the article topic, nuclear quadrupole resonance is similar to NMR except that, instead of using a magnetic field to induce an energy splitting (which gives you the Larmor frequency), you take advantage of electric field splitting instead. This only works in atoms that have a quadrupole moment, and the only one of those that's present at high concentrations in explosives (and living things too) is nitrogen-14.

WRONG - MOD PARENT DOWN (see inside) (1)

Alchemist253 (992849) | more than 7 years ago | (#17749632)

As someone who uses NMR literally every single day and has taken graduate courses in the subject, let me correct a few major issues with your statement.

1) "Doing it with a gradient field and a special pulse sequence lets you get the vibrational amplitudes of your protons based on their position within the gradient field." In NMR (NOT MRI), gradients most commonly come up the form of gradient shimming, which is a technique for homogenizing the magnetic field applied to a sample. In general, gradient fields themselves are undesirable (for chemical analysis; different needs arise in imaging). More importantly, you are confusing IR spectroscopy (which observes molecular vibrations) with NMR, which looks at quantum spin phenomena in nuclei. Briefly, dipolar nuclei (those with an odd number of protons and even number of neutrons; 1H is the best such nucleus for signal/noise ratio due to its high natural abundance and gyromagnetic ratio) distribute themselves into two quantum spin states (aligned/opposed to the incident field) roughly according to Maxwell-Boltzmann statistics due to the slight difference in energies of the states. The energy difference is on the order of RF energy, and the quantized absorption of RF radiation of the exact energy of the state differential can induce a spin state transition. The exact energy required depends primarily on the intrinsic properties of the nuclei, but also slightly on the electronic environment surrounding the nucleus, which permits (in NMR) chemically non-equivalent nuclei to be distinguished in a molecule. More complex experiments (an acronym soup that includes experiments such as DEPT, COSY, NOESY, HETCOR, etc.) can be used to elucidate the entire structure of a molecule, including distances between atoms. MRI is based, broadly speaking, on the fact that the amount of time it takes spin-excited nuclei to "relax" back to the ground state depends on factors including their solvent environment. Hence MRI can easily distinguish between, e.g., water and fat, by carefully observing how long an NMR signal is seen from excited nuclei.

2) "at varying radio-frequencies to see if there was any resulting resonance and output RF (radiofrequency) signal." When resonance is achieved the incident RF is absorbed, not emitted. Applying "varying" RF is classical "continuous wave" NMR. Modern spectrometers (FT-NMR) use a broad pulse to excite ALL resonances simultaneously. As they relax, RF is emitted as you suggest, and the probe coils detect the decaying resonances of all nuclei simultaneously. A computer then does a weighted Fourier transform on the time-resolved data to convert from time domain to frequency domain, thus extracting the spectrum. CW spectrometers have been completely replaced by FT instruments due to much shorter experiment times, better signal to noise, and ability to run multidimensional experiments.

3) "Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it." I don't even know where to begin. First, the proton resonance frequency is ENTIRELY dependent on the strength of the applied field. Hence the strength of the superconducting magnets in NMR spectrometers is usually measured by the standard proton resonance frequency in the magnet. For example, I usually use 400 MHz instruments, which means that the field is of such a strength that protons resonate around 400 MHz. I also have 500 and 600 MHz instruments available when I need greater resolution or signal/noise ratio. The primary difference between the instruments is the strength (read: size) of the cryomagnet. Furthermore, the highest power NMR commercially available recently was 900 MHz. I have heard that the major manufacturers (Bruker and Varian) have a 950 on deck, and it may now be for sale (for a hefty sum). They are still working on trying to reach 1 GHz. There are NMR spectrometers that have been reported to achieve the much higher 2.4 GHz resonance, but these are highly experimental prototypes developed at national labs and other special facilities; you're not going to find them in airports, hospitals, or chem labs anytime soon. Finally, microwave heating by NMR? NO! Microwave radiation excites ROTATION of molecules - not vibration or nuclear spin transition. Once excited, water MOLECULES (not H atoms in said molecules) relax back to their normal rotational state(s) by transferring energy into translational kinetic energy, i.e. heat.

Note that nuclei with an odd number of protons and an odd number of neutrons (e.g. deuterium and the abundant 14N) have a quadrapole moment as suggested by the article summary. It is possible to do NMR on such nuclei, but it's a pain and is rife with problems. (For one, screwy relaxation times of quadrapolar nuclei tend to wash out spin-spin coupling to other bonded nuclei, which can lead to spectral interpretation difficulties.) But as I said it CAN be done, and thus conceivably could be used in an explosives detection system. Honestly, though, I foresee problems ahead.

Re:WRONG - MOD PARENT DOWN (see inside) (1)

Rich0 (548339) | more than 7 years ago | (#17749834)

Agreed with you in general but the grandparent was right about the use of field gradients in MRI. In NMR as you indicated they tend to only be used for shimming, solvent suppression, and some more exotic experiments (I think diffusion measurements are one - molecule moves during experiment it is affected by gradient pulses - if it doesn't move pulses cancel out - possibly useful in measuring small molecule binding to big molecule).

MRI does use field gradients - because it needs some way of measuring T1/T2 relaxation as a function of position in 3D space. I'm certainly not an expert in MRI but I'm guessing the principle is that with a gradient the Larmor frequency varies with position in 3D space, so with a couple of pulses with varied gradients you can elucidate the contribution of any piece of 3D space to the overall signal, since they're all resonating at different frequencies (which of course are all measured separately at the same time on an FT-NMR). Wikipedia has a description of this - it is short on details but it seems reasonable.

I did cringe at the 2.4GHz reference. Microwaves excite electrons, NMR/MRI/NQR excite nuclei. Both have energy levels under various conditions (the latter need an external magnetic field for this), and so they are susceptible to spectroscopy. However, the mechanisms are very different, and the energies involved are very different as well (even in a very powerful field nuclei are only slightly reactive to RF, but electrons and photons go together with no effort at all).

Note - I'm a bit rusty on my NMR, and haven't been active in the field for a while, but I do have enough experience to be somewhat dangerous...

Re:nuclear resonance is MRI without the "imaging" (0)

Anonymous Coward | more than 7 years ago | (#17757086)

Protons resonate at 2.4 GHz approximately (which is the frequency used in microwaves to resonate the H's in the {H}_2{0} molecules in your food and heat it.

Nope. Protons resonate at higher frequencies, as do water molecules. 2.4 MHz is not where water absorbs the most energy. That's an urban legend. You want microwaves to enter to food and heat it inside. Please read this [lsbu.ac.uk] and stop spreading this false story.

Not all explosives contain nitrogen (4, Insightful)

dsci (658278) | more than 7 years ago | (#17746556)

And not all nitrogen containing explosives are white powders. :)

Re:Not all explosives contain nitrogen (0)

Anonymous Coward | more than 7 years ago | (#17749522)

Not all white powers are nitrogen based explosives either man, let me tell you a little bit more about myself and why I'm so fascinating to talk about, MAN there are a lot of people in this line, eh, so where are you going I'm going somewhere amazing *sniff*

Would be easier to just use sound waves. (1)

gearmonger (672422) | more than 7 years ago | (#17746648)

Beat the hell out of the bag. If you hear a "kaboom" (where's the kaboom? there's supposed to be an earth-shattering kaboom!), then there was a bomb in it. Simple.

Also helps greatly reduce the volume of checked and carry-on luggage.

This technique has been studied for a long time (1)

Jeff1946 (944062) | more than 7 years ago | (#17746664)

Prototype mine detectors based on NQR have been built and tested. The signals are very weak, even with tens of watts of excitation which makes this a difficult techique for practical use. See http://maic.jmu.edu/JOURNAL/9.2/RD/williams/willia ms.htm [jmu.edu] for more info.

Re:This technique has been studied for a long time (1)

calidoscope (312571) | more than 7 years ago | (#17747916)

The signals are very weak, even with tens of watts of excitation


Make that several kilowatts (peak) of excitation...


The maximum signal amplitude is directly proportional to the mass of material and inversely proportional to the absolute temperature (until you get to the micro-kelvin temperature). The effective noise is inversely proportional to the square root of the available signal averaging time and that time is a messy function of material, excitation power, receiver recovery time and temperature.


The novel aspect from TFA is the use of SQUIDs for detection which would, under ideal conditions, reduce the noise and thus improve detection performance. The reality is that SQUIDs buy very little in noise performance since most of the noise picked up by a conventional NQR detector comes from either the Johnson noise of the coil or target (room temperature electronics can be made to have a noise temperature of a few Kelvin). The coil noise can be reduced by cooling the coil, but that will come for naught if the target is lossy (e.g. wet soil).

Only thing new is using a SQUID (3, Informative)

calidoscope (312571) | more than 7 years ago | (#17746676)

Research into using NQR for explosive detection dates back to the 1970's. The first NQR baggage scanner was built by Al Garroway's group at NRL in the early 1990's using room temperature coils and room temperature electronics.


Ron Sager and Alan Sheldon of Quantum Design used a SQUID in 1992 for detecting the NQR response of ammonium perchlorate (~38kHz), so the Japanese group isn't even the first to use SQUIDs for NQR...

boom (0)

Anonymous Coward | more than 7 years ago | (#17746748)

Even if it doesn't find the explosives, I'll bet it's great at finding the detonators.

much simpler method (2, Insightful)

AlgorithMan (937244) | more than 7 years ago | (#17747026)

I have a much simpler method: if america doesn't like country X it follows that X has explosives...

Useless against several explosives (1)

j. andrew rogers (774820) | more than 7 years ago | (#17747092)

Having yet another nitrogen explosives detector is not very interesting. It does not solve the problem of peroxide and oxyhalide based explosives, the former having already proven to be popular with terrorists, and both types having seen limited military application in the 20th century.

A truly effective explosives detection technology will need to target a broader range of high explosive chemistries, and preferably not the same ones over and over. When the corner store is out of C4, people bent on blowing things up will find something else.

Re:Useless against several explosives (1)

Slashamatic (553801) | more than 7 years ago | (#17750938)

Most explosves are based on nitrates, especially commercial ones because of their stability and energy density. Yes, the bad guys can move to something else, but it makes manufacture more difficult and increases the risk of detonation before deployment or squibs (the chappati bombs used in the UK).

How about explosive without nitrogen? (1)

Cyberax (705495) | more than 7 years ago | (#17747276)

And how about explosives without nitrogen? I personally know two high explosives, which were successfully used in WWII and which doesn't contain nitrogen.

And I also know some other compounds that can serve as explosives and does not contain nitrogen or chlorine.

And I'm not a professional chemist, chemistry was just my hobby at school and high-school.

Re:How about explosive without nitrogen? (1)

somepunk (720296) | more than 7 years ago | (#17747478)

Bzzzt. Fat Man and Little Boy were tiggered using high powered nitrogen based (TNT or similar) explosives.

Perhaps you had some others in mind, but these are what will pop into people's minds.

Re:How about explosive without nitrogen? (1)

Cyberax (705495) | more than 7 years ago | (#17751346)

Nope. There was another explosive, which was used in landmines. It can be fairly easy synthesized in any laboratory (I synthesized small quantities for different pranks).

Great! (0)

Anonymous Coward | more than 7 years ago | (#17747472)

From TFA:
"Scientists in Japan have developed a new technique for sensing explosives in luggage and landmines."

Thank goodness - a safe way to tell if a landmine contains explosives. That'll save a lot of wear and tear on orphans.

Hey Great! (1)

gp310ad (77471) | more than 7 years ago | (#17747734)

Now I won't have to deal with homeland security cutting open my 5lb bag of grits anymore when I leave The South for work.

I've seen this in the movies all the time.... (1)

sniepre (517796) | more than 7 years ago | (#17747796)

You just have to send the correct frequency, and bam, it explodes!

It would be easier... (1)

delvsional (745684) | more than 7 years ago | (#17749368)

When are we going to bypass this whole mess and just invent the teleporter?

Re:It would be easier... (1)

tehcyder (746570) | more than 7 years ago | (#17753096)

When are we going to bypass this whole mess and just invent the teleporter?
But then the evil terrorists could beam explosives/small nukes anywhere they wanted to.

You haven't really thought this through, have you?

Nitrogen detector....bathed in Nitrogen! (1)

Muad'Dave (255648) | more than 7 years ago | (#17750450)

The SQUID operates at a temperature of 77 Kelvin (minus 196 degrees centigrade) which we achieve by using liquid nitrogen.

Wouldn't it be difficult to detect small amounts of nitrogen bound in substances when your SQUID detector is bathed in the same substance you're trying to detect?

Great Idea. Blow them up with the transmitters. (0)

Anonymous Coward | more than 7 years ago | (#17751758)

Besides possibly denotating some explosive devices this technique can be tailed to detect Vista outbreaks.

but... (1)

markana (152984) | more than 7 years ago | (#17754756)

>distinguish between different white powders

I would think that black powder would be more of a concern here...

Misleading & naive article (1)

sciguy123 (1056876) | more than 7 years ago | (#17793530)

There is nothing new about using radio waves for explosives detection. The navel research labs and russians have been working on NQR explosives detection for 40 years. Many other groups worldwide are also working on the technology. Two companies have products out and in airports, GE and QR Sciences, although currently the number of units deployed is quit low. The somewhat novel thing in the article is the use of squids. This is not entirely novel because the russian, GE and others have looked at this over the past 10 years. It is generally accepted that squids generally do not add much improvement to the signal to noise ration, SNR, in the lab, and add NOTHING to fieldable configurations of NQR systems. This is because the major noise sources are not the amplifier itself, but rather the intrinsic antenna noise, RFI (radio frequency interference), and induced ringing in the target item (shoes, baggage content, etc). Additionally the squids add significant cost, complexity, and reliablility issues. What this japanese group has done is all well and fine for research in a highly controlled laboratory environment, but it is completely unreasonable to tout this as useful in real life applications, much less presenting it as a breakthru.
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