I installed mod_security on my server a few weeks ago with a few simple regexes to cover the more prolific referrer spammers recorded by awstats. Set the mod_security default action to deny,status:412. Then in httpd.conf I set the ErrorDocument for the 412 code to an empty file.
Now when the referer spammer hits my site, they get denied and get nothing back. Bandwidth wasted serving up pages to referer spammers is cut to virtually nil. The spammers are still there banging away and a few still get by though. The list of referrers needs to be monitored so that new mod_security rules can be added as required. That's no different than using mod_rewrite to deny the referrer spammers though.
Re:Better than a Volcano
on
Hacking Vodka
·
· Score: 2, Funny
this will work with many other alcohols too. On a houseboating trip, one of my friends in a fit of inebriated creativity came up with a variant of this trip where he stuck the flaming shot glass to his ass. We called it a "Butt-buca", since the drink it was being done with was Sambuca.
Once, while showing the trick off at a house party, my friend left it on too long an it got stuck to his ass. We were all laughing so hard at him running around yelling "It's stuck! It's stuck! Get it off!" none of us could help him (we were all rolling around on the ground in pain from busting a gut laughing). And those of us who were still able to stand didn't want to get anywhere near his ass to extract the shot glass.
It seems a group of scientists at LLNL, Los Alamos and Argonne have data from a couple of years ago that challenges the principles behind this gamma ray weapon.
Using the Advanced Photon Source at Argonne, which has more than 100,000 times higher X-ray intensity than the dental X-ray machine used in the original experiment, and a sample of isomeric Hf-178 fabricated at Los Alamos, the team of physicists expected to see an enormous signal indicating a controlled release of energy stored in the long lived nuclear excited state. However, the scientists observed no such signal and established an upper limit consistent with nuclear science and orders of magnitude below previous reports.
...
The team set out to verify previous findings that stated a nuclear isomer, (hafnium) Hf-178, which has a half life of 31 years, is able to release a controlled amount of energy (decay quicker) when tickled with dental machine X-rays. However, when the team turned the APS X-ray beam onto the sample of 31-yr. Hf-178, no detectable increase of the isomer decay occurred. In other words, the X-ray irradiation did not decrease the time it takes for hafnium to decay; a result that Becker and the team claim is consistent with nuclear physics.
the inventor of the Gatling gun had similar ideas. He thought that if he could create a weapon that was so devastating to use, nobody would want to go to war anymore. We all know where that led.
A similar kind of filter is also used in CT scanners used on patients. It's called a butterfly filter, because of it's shape and does the same purpose: Attenuate the portion of the beam passing through the periphery of the body more than the portion of the beam passing through the center. That way the x-ray flux at the detector is more or less normalized, and you don't get huge variations in x-ray intensity across the length of the detector.
In the early days of CT, when it was first developed and only heads were scanned, it was normal to place the patient's head in what was essentially a bag of water so that the x-ray beam would be scanning through a more or less uniform field. Imagine taking a large garbage bag filled with water, and resting it on your head so it surrounds the top of your head.
It sounds like the thing is intended as a screening device, so it's not going to tell you where it is. Maybe in the future, but as with all screening methods (mammography being the most common), it's intended to check a lot of people quickly and non-invasively. If something suspicious is found, then follow-ups are done using more detailed and possibly more invasive methods.
Perhaps the most important part of the NewScientist article is at the bottom
the results of the early trials have yet to appear in a peer-reviewed medical journal and must be regarded with caution until then.
This happened to our brand new 3T magnet. A nurse attending a patient decided to pull a chair into the room so she could sit down. There were already wooden chairs in the room, but for some reason the person decided this chair would be better.
The magnet was down for about 3 days while service engineers tried to figure out how to minimize damage to the magnet while extracting the chair
Burns from MRI scans are rare, but entirely possible, especially with patients connected to monitoring equipment. The important thing when dealing with wired patients is to make sure none of the wires or leads form any kind of loop. Otherwise you end up with a classic implementation of Maxwell's laws and induce currents and heating in the looped lead, resulting in a burn potential.
This happened recently in the hospital I work at, and while the patient wasn't seriously injured, it did cause a bit of a stir.
Based on what I've read of the 3200+ at Tom's Hardware and Tech Report, the CPU performance is good, just slightly better than the 3000+, but still gets trumped by the P4 3.0 and 3.06 CPUs. Both call into question the validity of AMD's CPU rating system, and judging from their benchmarks, rightly so. The 3200+ is also supposed to be more expensive than the P4s, which combined with the dissapointing performance may limit it's popularity.
It will be interesting to see how the 3200+ performs when overclocked.
I recall my first eclipse experience when I was in 3rd grade. All the windows were covered over, the curtains were drawn, and nobody was allowed outside. The school was sealed up tight. Observation areas were set up at some windows with a piece of welder's glass so students could take a peek at the eclipse.
We were of course warned that we shouldn't look at the sun during the eclipse, but the overall impression that most of my fellow students were left with was that being outside during an eclipse was dangerous, like somehow the sun had changed and the light would cause people to go blind or something.
Better to be safe than sorry I suppose, but I recall a few friends getting nervous during the next eclipse several years later.
it's not a million amps the nanotubes are carrying. The article refers to a current density of a million amps/cm^2. A pretty hefty current density, but taking the size of the nanotube into account, the actual current it's carrying is probably pretty small (but big for something of it's size).
I would suspect that the patient was getting a cardiac study with Tl-201. In the body, Tl-201 has an effective half life of roughly 6-8 days. It's entirely possible for there to be sufficient Tl-201 left even after 3 weeks for it to trigger a portal monitor.
If the cardiac study was performed using Tc-99m (half life of 6 hours, effective half life in the body of about 3-5), there is no way this amount would have set off the monitors after 3 weeks. The patient must have had some other procedure in between then in this case.
the detectors being used are quite likely a sodium iodide scintillator detector, which can be made exquisitely sensitive. There have been similar issues at landfills equipped with radiation detectors. There are several cases where a garbage truck has tripped off the alarms, sending people into a flurry of activity to figure out where the radioactive trash came from and sending it back to the person, usually a patient or a hospital.
These kinds of incidents are becoming a little less common with better training of the people manning the monitors. Train them to recognize which ones are medically used isotopes and can be safely ignored.
Should be able to give the same training to whoever runs the subway monitors.
radioiodine therapy is not chemotherapy, nor is it brachytherapy. chemotherapy is the use of cytotoxic chemicals (none of which are radioactive) to kill cancer cells at a faster rate than normal cells. Brachytherapy is the implantation of radioactive sources into a tumour to kill them.
Radioiodine therapy is a form of radioisotope therapy.
there is also radioimmunotherapy, which uses monoclonal antibodies usually labelled with a beta emitter to deliver targeted radiation to a specific antigen expressing tumour.
I got a Visor Platinum for Xmas just about 2 years ago. This was after spending a couple of years waffling on deciding whether I wanted one or not. My very first impression of them was that they were just geek status symbols.
At first, I didn't think I was going to get much use out of my Platinum, but once I started playing with it and using it, there was definitely potential in it.
The real kicker for me was when I bought a copy of QuickOffice and got myself a Stowaway keyboard. That combination has allowed me to pretty much do away with carrying around my laptop, especially for work, where I do a lot of data collection during equipment testing. Now instead of lugging around a big laptop, I've got my Visor and folded up Stowaway, which isn't much larger than the Visor.
If you can find that 'killer PDA app' that makes it useful, then it becomes an indispensible tool. For me, it was Quicksheet. For others it might be something else...document editing, bar code scanning, databases, whatever.
To the people who bought a PDA that just sits unused in drawer, take it out again, dust it off and browse sites like palmgear.com or whatever PocketPC software sites there are. Think about what else you would want to do with it besides the standard PIM functions. Chances are there's probably something out there that will let you do it.
Along with computer/electronics recycling being not so good for the environment, add making computer chips to it as well. According to an article in the Nov 16, 2002 issue of Science News (abstract online. Full text available if you're a subscriber or from your local library),
A new analysis reveals that the production of a single 2-gram microchip requires nearly 2 kilograms of chemicals and fossil fuels.
According to the article, making a single computer chip takes a lot of chemicals (including hydrogen fluoride), and a lot of fossile fuel, making the process an incredible resource hog for what we get out of it.
There isn't much in the article about what happens to all the chemicals used though (i.e. how they're disposed of, if they're reclaimed/recycled).
and of course after i've written the above and gone to read the PDF again, i see where the strangeness is.
0.5 mm lead should be more than sufficient to stop all of a 50 kV x-ray beam and most of a 70 kV beam.
I certainly wouldn't expect 0.5 mm lead to stop all of a 60 keV gamma ray source though. Most of it definitely.
However, the document doesn't go into any of the details of how the material was tested. But still, it does raise some questions.
then again, the x-ray part of the table mentions broad beam apparatus, which means scatter radiation was included. including scatter radiation makes it look like more radiation reached the detector, decreasing the apparent blocking ability.
this would probably account for why their 50 kV beam was only partially attenuated instead of fully, and why the other x-ray energies aren't blocked as much as they should have been.
The mistake they're making is not mentioning that their x-ray source is probably polyenergetic (getting a mono-energetic x-ray source is somewhat difficult) and contains a wide spectrum of x-ray energies.
Most gamma ray sources tend to be mono-energetic, so if you have a source of 60 keV (kiloelectronVolts) gamma rays, that's all you have. On the other hand, if you have a 60 kV (kiloVolts) x-ray source (the tube operating potential) you have x-rays anywhere from 10-60 keV, with most of them probably around 25-40 keV. The effective energy of this beam will be around 30 keV.
Note the distinction in units. Subtle but very different.
Getting back to the difference in absorption, since the x-ray beam has a much higher proportion of low energy photons compared to the gamma ray source, more of these will be absorbed by the material. Thus more of the x-ray beam would be absorbed, compared to the gamma ray source.
Their results aren't bogus...they're just comparing apples and oranges (which may be just as bad).
Error #2: X-rays and gamma rays are both photons; they're only distinguished by their energies
The distinction between x and gamma rays is their origin.
gamma rays are nuclear in origin, resulting from the decay of radionuclides.
X-rays are electronic origin, generated when an electron loses energy in some fashion (i.e. moving from a higher energy level to a lower energy level).
aside from that, there is no way to tell a gamma photon from an x-ray photon.
anybody who's studied radiation interactions with matter will tell you that for gamma/X rays, it's not the density (g/cm^3) of the material but the electron density (electrons/cm^3) that determines the attenuation properties of a material. Generally, metals with a higher atomic number (Z) have more electrons, so they usually have better attenuation properties.
As it turns out, sometimes you can pack lighter weight nuclei close enough together that you get a similar electron density to metals (or even higher sometimes). this is probably what they've done with this 'polymer'. Althogh on a mailing list I'm on, someone mentioned that the material was just fabric that had been soaked in a barium solution and dried. Whether that was true or not was never establised though.
There is one incorrect statement in the article though.
"The helium nuclei that make up alpha radiation have so little energy that almost any physical barrier can stop them."
Alpha particles can be emitted with extremely high energies, upwards of 10 MeV. What makes alpha particles so non-penetrating is their charge. Their +2 charge causes them to interact very strongly with neighbouring electrons, which causes them to lose energy quickly. That's also the reason why there isn't any special shielding necessary for alpha particles. Most alpha particles will be stopped in the dead layer of your skin, and therefore pose little external hazard. What makes alpha particles dangerous is if they become internalized (inhaled or ingested). The fact they lose energy quickly means that energy is transferred to whatever material it happens to collied with, causing much damage in the process.
the 2D bar codes showed up in later volumes of Nibble and were placed towards the back of the magazine or the end of the article. They were a nifty idea, but like others i'm sure, I couldn't afford the reader. I relied on the line by line checksums at the end of each article to help me track down typos. Especially useful for some of those assembly programs.
Slashdot Mirror
I installed mod_security on my server a few weeks ago with a few simple regexes to cover the more prolific referrer spammers recorded by awstats. Set the mod_security default action to deny,status:412. Then in httpd.conf I set the ErrorDocument for the 412 code to an empty file.
Now when the referer spammer hits my site, they get denied and get nothing back. Bandwidth wasted serving up pages to referer spammers is cut to virtually nil. The spammers are still there banging away and a few still get by though. The list of referrers needs to be monitored so that new mod_security rules can be added as required. That's no different than using mod_rewrite to deny the referrer spammers though.
this will work with many other alcohols too. On a houseboating trip, one of my friends in a fit of inebriated creativity came up with a variant of this trip where he stuck the flaming shot glass to his ass. We called it a "Butt-buca", since the drink it was being done with was Sambuca.
Once, while showing the trick off at a house party, my friend left it on too long an it got stuck to his ass. We were all laughing so hard at him running around yelling "It's stuck! It's stuck! Get it off!" none of us could help him (we were all rolling around on the ground in pain from busting a gut laughing). And those of us who were still able to stand didn't want to get anywhere near his ass to extract the shot glass.
Read the story here
Excerpts from the story:
the inventor of the Gatling gun had similar ideas. He thought that if he could create a weapon that was so devastating to use, nobody would want to go to war anymore. We all know where that led.
A similar kind of filter is also used in CT scanners used on patients. It's called a butterfly filter, because of it's shape and does the same purpose: Attenuate the portion of the beam passing through the periphery of the body more than the portion of the beam passing through the center. That way the x-ray flux at the detector is more or less normalized, and you don't get huge variations in x-ray intensity across the length of the detector.
In the early days of CT, when it was first developed and only heads were scanned, it was normal to place the patient's head in what was essentially a bag of water so that the x-ray beam would be scanning through a more or less uniform field. Imagine taking a large garbage bag filled with water, and resting it on your head so it surrounds the top of your head.
Perhaps the most important part of the NewScientist article is at the bottom
it's never wise to bypass the metal detectors even if you don't think the object is ferro or diamagnetic.
r 01 .jpgC hair02 .jpg
http://radinfo.musc.edu/images/photos/MRIvsChai
http://radinfo.musc.edu/images/photos/MRIvs
This happened to our brand new 3T magnet. A nurse attending a patient decided to pull a chair into the room so she could sit down. There were already wooden chairs in the room, but for some reason the person decided this chair would be better.
The magnet was down for about 3 days while service engineers tried to figure out how to minimize damage to the magnet while extracting the chair
Burns from MRI scans are rare, but entirely possible, especially with patients connected to monitoring equipment. The important thing when dealing with wired patients is to make sure none of the wires or leads form any kind of loop. Otherwise you end up with a classic implementation of Maxwell's laws and induce currents and heating in the looped lead, resulting in a burn potential.
This happened recently in the hospital I work at, and while the patient wasn't seriously injured, it did cause a bit of a stir.
Based on what I've read of the 3200+ at Tom's Hardware and Tech Report, the CPU performance is good, just slightly better than the 3000+, but still gets trumped by the P4 3.0 and 3.06 CPUs. Both call into question the validity of AMD's CPU rating system, and judging from their benchmarks, rightly so. The 3200+ is also supposed to be more expensive than the P4s, which combined with the dissapointing performance may limit it's popularity.
It will be interesting to see how the 3200+ performs when overclocked.
I recall my first eclipse experience when I was in 3rd grade. All the windows were covered over, the curtains were drawn, and nobody was allowed outside. The school was sealed up tight. Observation areas were set up at some windows with a piece of welder's glass so students could take a peek at the eclipse.
We were of course warned that we shouldn't look at the sun during the eclipse, but the overall impression that most of my fellow students were left with was that being outside during an eclipse was dangerous, like somehow the sun had changed and the light would cause people to go blind or something.
Better to be safe than sorry I suppose, but I recall a few friends getting nervous during the next eclipse several years later.
it's not a million amps the nanotubes are carrying. The article refers to a current density of a million amps/cm^2. A pretty hefty current density, but taking the size of the nanotube into account, the actual current it's carrying is probably pretty small (but big for something of it's size).
I think the replacement units are going to be without the battery, making them significantly lighter to ship.
The instructions you get when registering your recalled unit for replacement tell you to remove the battery to use it in the replacement unit.
The external radiation that's being detected are bremsstrahlung x-rays being produced as the P-32 beta particles collide and lose energy.
I would suspect that the patient was getting a cardiac study with Tl-201. In the body, Tl-201 has an effective half life of roughly 6-8 days. It's entirely possible for there to be sufficient Tl-201 left even after 3 weeks for it to trigger a portal monitor.
If the cardiac study was performed using Tc-99m (half life of 6 hours, effective half life in the body of about 3-5), there is no way this amount would have set off the monitors after 3 weeks. The patient must have had some other procedure in between then in this case.
the detectors being used are quite likely a sodium iodide scintillator detector, which can be made exquisitely sensitive. There have been similar issues at landfills equipped with radiation detectors. There are several cases where a garbage truck has tripped off the alarms, sending people into a flurry of activity to figure out where the radioactive trash came from and sending it back to the person, usually a patient or a hospital.
These kinds of incidents are becoming a little less common with better training of the people manning the monitors. Train them to recognize which ones are medically used isotopes and can be safely ignored.
Should be able to give the same training to whoever runs the subway monitors.
radioiodine therapy is not chemotherapy, nor is it brachytherapy. chemotherapy is the use of cytotoxic chemicals (none of which are radioactive) to kill cancer cells at a faster rate than normal cells. Brachytherapy is the implantation of radioactive sources into a tumour to kill them.
Radioiodine therapy is a form of radioisotope therapy.
there is also radioimmunotherapy, which uses monoclonal antibodies usually labelled with a beta emitter to deliver targeted radiation to a specific antigen expressing tumour.
I got a Visor Platinum for Xmas just about 2 years ago. This was after spending a couple of years waffling on deciding whether I wanted one or not. My very first impression of them was that they were just geek status symbols.
:)
At first, I didn't think I was going to get much use out of my Platinum, but once I started playing with it and using it, there was definitely potential in it.
The real kicker for me was when I bought a copy of QuickOffice and got myself a Stowaway keyboard. That combination has allowed me to pretty much do away with carrying around my laptop, especially for work, where I do a lot of data collection during equipment testing. Now instead of lugging around a big laptop, I've got my Visor and folded up Stowaway, which isn't much larger than the Visor.
If you can find that 'killer PDA app' that makes it useful, then it becomes an indispensible tool. For me, it was Quicksheet. For others it might be something else...document editing, bar code scanning, databases, whatever.
To the people who bought a PDA that just sits unused in drawer, take it out again, dust it off and browse sites like palmgear.com or whatever PocketPC software sites there are. Think about what else you would want to do with it besides the standard PIM functions. Chances are there's probably something out there that will let you do it.
Or else send it to me
According to the article, making a single computer chip takes a lot of chemicals (including hydrogen fluoride), and a lot of fossile fuel, making the process an incredible resource hog for what we get out of it.
There isn't much in the article about what happens to all the chemicals used though (i.e. how they're disposed of, if they're reclaimed/recycled).
and of course after i've written the above and gone to read the PDF again, i see where the strangeness is.
0.5 mm lead should be more than sufficient to stop all of a 50 kV x-ray beam and most of a 70 kV beam.
I certainly wouldn't expect 0.5 mm lead to stop all of a 60 keV gamma ray source though. Most of it definitely.
However, the document doesn't go into any of the details of how the material was tested. But still, it does raise some questions.
then again, the x-ray part of the table mentions broad beam apparatus, which means scatter radiation was included. including scatter radiation makes it look like more radiation reached the detector, decreasing the apparent blocking ability.
this would probably account for why their 50 kV beam was only partially attenuated instead of fully, and why the other x-ray energies aren't blocked as much as they should have been.
The mistake they're making is not mentioning that their x-ray source is probably polyenergetic (getting a mono-energetic x-ray source is somewhat difficult) and contains a wide spectrum of x-ray energies.
Most gamma ray sources tend to be mono-energetic, so if you have a source of 60 keV (kiloelectronVolts) gamma rays, that's all you have. On the other hand, if you have a 60 kV (kiloVolts) x-ray source (the tube operating potential) you have x-rays anywhere from 10-60 keV, with most of them probably around 25-40 keV. The effective energy of this beam will be around 30 keV.
Note the distinction in units. Subtle but very different.
Getting back to the difference in absorption, since the x-ray beam has a much higher proportion of low energy photons compared to the gamma ray source, more of these will be absorbed by the material. Thus more of the x-ray beam would be absorbed, compared to the gamma ray source.
Their results aren't bogus...they're just comparing apples and oranges (which may be just as bad).
The distinction between x and gamma rays is their origin.
gamma rays are nuclear in origin, resulting from the decay of radionuclides.
X-rays are electronic origin, generated when an electron loses energy in some fashion (i.e. moving from a higher energy level to a lower energy level).
aside from that, there is no way to tell a gamma photon from an x-ray photon.
doh, yes of course that's what i meant. thanks for clarifying.
As it turns out, sometimes you can pack lighter weight nuclei close enough together that you get a similar electron density to metals (or even higher sometimes). this is probably what they've done with this 'polymer'. Althogh on a mailing list I'm on, someone mentioned that the material was just fabric that had been soaked in a barium solution and dried. Whether that was true or not was never establised though.
There is one incorrect statement in the article though.
Alpha particles can be emitted with extremely high energies, upwards of 10 MeV. What makes alpha particles so non-penetrating is their charge. Their +2 charge causes them to interact very strongly with neighbouring electrons, which causes them to lose energy quickly. That's also the reason why there isn't any special shielding necessary for alpha particles. Most alpha particles will be stopped in the dead layer of your skin, and therefore pose little external hazard. What makes alpha particles dangerous is if they become internalized (inhaled or ingested). The fact they lose energy quickly means that energy is transferred to whatever material it happens to collied with, causing much damage in the process.
i hope you're just joking.
metal detectors work by generating an electromagnetic field, and sensing any disruptions caused by the movement of metal objects through the field.
the 2D bar codes showed up in later volumes of Nibble and were placed towards the back of the magazine or the end of the article. They were a nifty idea, but like others i'm sure, I couldn't afford the reader. I relied on the line by line checksums at the end of each article to help me track down typos. Especially useful for some of those assembly programs.