Relatively popular is somewhat pushing it. The overwhelming majority of people have never been horse riding. "It is only relatively popular amongst MPs and vastly rich powerful people and travellers" two of this group were outraged.
some CRTs went higher than that. However even with no shielding the dose rate would be too low to be a weapon. Admittedly you might not want to sit in front of it for years..
The clue being the heat. In the X-ray range 1% of the electron beam is converted to X-rays the rest to heat. This is why X-ray tubes are either on for short periods, water cooled or have massive metal anodes.
Just a bit more than a typical microwave oven. You oven can go to about say 300 degrees celsius equivalent to about 0.05 eV.
To ionize oxygen or hydrogen (13.6 eV) by heating well that's going to take about 158,000 degrees. The long and the short of it being that ionization by heating is not easy.
I also notice the list of representatives include folk from Npower, BP, CBI and the US Embassy. Not exactly the standard sources of hardcore left wingers. Still best to gloss over these folk as focusing on them may not fit in with the promotion of FUD.
Clearly a generally pro science network supporting the scientific consensus is an important tale that absolutely warrants such a massively informed debate.
I would imagine it would be far far easier to breed (or use GM techniques) to make a crop plant that can deal with what is effectively a super short season than to attempt to light up the night. You could even store some of the daytime heat and smooth the "seasonal" temp transitions using a high heat capacity plastic mixed into the soil.
Given tundra based trees survive months with no usable light due to thick snow cover and natural summer annuals often only get light for growth for a few weeks a year this doesn't seem the biggest issue with moon farming.
The main advantage of computer driven cars is that they learn faster than humans. A human is at a massive learning disadvantage as he can't exactly replicate his actions, recall his sensory input perfectly, vary aspects of his driving without affecting other aspects nor make changes that are smaller than his biologically imposed resolution limit. The computer can learn more from every previous race and try more things in the search for lower lap times. After sufficient versions/updates (and assuming a sporting governing body doesn't implement blocking rules) the AI's ability will exceed the upper limit imposed by the biology of the driver.
I can't see any other way this could possible work out.
So you think that lethal accidents are caused by a minority of very bad drivers. Very bad as in not mere speeding or not paying attention as almost everyone does occasionally. That would be interesting if true. Do you have any stats. or links to back that up?
I would (perhaps naively) have assumed that most types of non trivial road accidents have a chance of lethality. So I wouldn't expect those involved in lethal accidents to have a significantly different ability distribution to normal accidents.
Damn straight, why worry about the safety of yourself or others when you can be having fun.
For Americans death by car accident is about a 1 in 100 lifetime chance not massive but hardly minuscule. If you could say half that is that not a reasonable thing to do.
Thou of course everyone is an above average driver so the odds don't apply to them.
I once mentioned shielding to a X-ray laser physicist who was talking about his high energy X-ray laser. "Aren't you worried about shielding?". The reply "O no our X-rays don't go that far in air."
That's when I realized that laser physicists have a slightly different interpretation of high-energy than most radiation physicists. I only consider high energy X-rays those at 100 keV+.
Sort of killing the buzz here but if you read the paper and maybe look at figure 2B you will see why this technique (high-harmonic generation) cannot be extended to be usable at higher keV beam without the laws of physics changing. At the current higher end their efficiency has fell to what 0.01% and falling fast.
I don't see how you can blame Google for an Apple led consortium giving a load of their patents to a massive patent troll (after promising to license them reasonably). You can blame Google and Intel for pushing up the price that's about it.
It would surprise me and most Atomic physicists. The exact made up of weapon components is secret but the interactions of X-rays with matter, even hot dense matter is not and such experiments are well within the domain of even an average university lab.
It's too small to be useful in tradition lens applications. Even at lower X-ray/Gamma energies when the refractive index is much bigger ( see: http://henke.lbl.gov/optical_constants/getdb2.html) you can't really use make reasonable lens.
It would be far far easier to increase the "commonly" available divergent sources' intensity than attempt to recover losses due to divergence with such a weakly focusing system. Hell, you could likely achieve a much bigger intensity increase by moving the source closer.
Can anyone even think of the medical imaging system they are envisaging. I assume they mean a phase-contrast approach but that needs a intense 700kV source with a small spot size and thin structured grating that absorb 700kV photons (which I don't think exist thou it's maybe just about within the capacity of man to make them).
The only application I can think of for this is for X-ray telescopes and astrophysics where you can't increase the source but you can have massively long imaging systems. However I will bet that their are not many interesting astrophysical events that emit only 700kV+ photons and the attenuation of the massive silicon lens may well counteract the benefit of the focusing.
The immediate never mind long term carcinogenic effect of very low dose radiation is not settled either way even in the simple case of cells. You can trudge through the related links and responses to them at: http://en.wikipedia.org/wiki/Radiation_hormesis
if you want to bore yourself.
The problem is it's very difficult to detect the difference between a small negative effect and a similarly sized positive one. Plus due to complicating effects like the bystander one it is likely that the pattern, flux and nature of the applied radiation will complicate the results.
At such low radiation levels in more complex organisms to know for certain you would need to have an unethical massive experiment using millions of animals with half being irradiated in a precisely controlled way. Rightly so this doesn't happen and so researchers have to look at smaller samples often with massive variations between them. Which is why the issue is not settled.
O and all radiation isn't bad, look at radiotherapy:-)
Couldn't agree more on the terminology. Eg phase-shift,interference,diffraction,scattering all used to describe similar things in different fields.
Yes I did wonder about double slit experiments (started in Atomic physics) but more so about the pattern's mere existence for single photons. The question of its shape seems trivial by comparison.:-) But thats for another board.
Okay sorry my mistake I thought you meant a direct phase measurement.
IMHO they are exactly doing a classic optic phase-constrast technique. Not exactly the same geometry as in microscopes due to the vastly superior optical beam available. But very similar and identical to the one often used for accelators X-ray CT which is why they reference this research. If you think this is wrong thats fine, I just disagree.
Ah okay, I understand what you mean now. However I still think your wrong as whilst you can measure phase of photons in the RF/Microwave domain there is no method of measuring phase directly with optical photons never mind 100keV electrons.
Indirectly by observing the imaging pattern (like a classic optical fringe pattern) the phase-shift can be done. Thou you might have to manipulate the beams to make the pattern more obvious as in classic interferometers or classic phase-contrast microscopy. Or you can look from "far" enough away so that the scattering from the phase-shift is enough to produce an image from which you can infer the phase-shift itself. This is the technique the Sheffield electron folk, some telescope folk and the X-ray folk can use. There is actually a smooth continuum of techniques depending on how far away your detector is, now transparent you object is and now you block or deal with the transmission image that "contaminates" the pure scatter/phase-shift image. But lets ignore the other fields for now as this is a semantic debate.
In this particular case they are not measuring the phase of the electron wave. They use a Gatan, Inc. ORIUS SC200 CCD Camera. Such a detector doesn't even detect the electrons directly. Instead it detects the 10 or so optical photons emitted from the scintillator placed in front of a CCD when each electron strikes it (the optical photons are of course emitted with random phase). So all they can possibly detect is an electron intensity profile. As this is a far field diffraction pattern you can mathematically reconstruct the sample that would produce it.
They themselves point on page 2 left column that this technique has been about for 40 years in the optical world and admit X-ray researchers have looked into it before.
I have done optical super resolution microscopy myself but have never heard about the MRI equivalent. Then again I don't really know much about MRI research so that's not so surprising and I obviously defer to your knowledge on this. Similarly I have seen synthetic aperture talks but only those done with Ultra sound or telescope based data.
Interesting now all the very different imaging modalities have vastly different implementation rates for similar techniques. Whilst the method and technology of acquisition is responsible for some of this I suspect a lot of it is researchers simply not knowing what is going on in other fields. (As I myself demonstrate with MRI)
Okay take your point on the MRI. I'd describe that as phase encoding spatial information rather than interference but I accept your way is just as valid.
It's certainly not the most common method in X-ray phase-constrast CT. However this method is used for X-ray CT at synchrotrons.
That's not true. When a physicist (like me) talks about an interferometer generally we mean a device that can measure phase shift or relative phase by comparing a beam with unknown phase to a separate known phase-shift reference beam.
See: http://en.wikipedia.org/wiki/Interferometry
Such interferometers (which normally use a point detector and therefore aren't measuring a pattern) have been about for well over a hundred years
See: A. Michelson, E. Morley. American Journal of Science: 333–345. (1887). So I simply don't know what you mean by "traditionally done".
Inferring phase-shifts from diffraction patterns is different (but obviously mathematically related) and more limited. For example a light beam going normally through a thin sheet of glass has no diffraction pattern. However it has a measurable phase-shift with an optical interferometer.
When you say we can only recently measure phase at high frequency for light I think I am missing something. If you are clever with the optics you can make all phase-shifts manifest as intensity variations. This is exactly the principle of a phase-contrast optical microscope widely available since the 60s.
Saying you don't need a lens is just wrong. At the very very least you need a lens to focus the beam onto the specimen.
O and if you actually read the paper you'll see that on the right hand column of page 5 all the current experimental limitations on resolution are listed. That the lens doesn't feature doesn't mean it follows that it is just down to wavelength, it's not. There is no lens in any hospital X-ray systems and your 100 keV diagnostic X-rays does not give you ~0.01nm resolution images. There is a world of difference between physics based resolution limits and that which can actually be obtained in most cases.
The method is nice, worthy of a nature paper and will improve on the future. However those that are saying that this is it "they got this" for imaging are just plain wrong. It's a new imaging modality we get one every couple of years or a few a year depending on your definition.
nMR measures the spectrum of RF emitted when nuclei excited into alignment by resonant RF pulses relax out of alignment with an externally applied magnetic field. MRI which is the correct name for the imaging modality measures the pattern of this RF emission. Maybe I am missing something but now exactly is this an interferometric process?
As to how this IS used in a research CT scanners google "phase-constrast CT". O and you want to do this in future to reduce patient dose or highlight soft-tissue boundaries which aren't obvious on a standard CT.
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Relatively popular is somewhat pushing it. The overwhelming majority of people have never been horse riding. "It is only relatively popular amongst MPs and vastly rich powerful people and travellers" two of this group were outraged.
some CRTs went higher than that. However even with no shielding the dose rate would be too low to be a weapon. Admittedly you might not want to sit in front of it for years..
The clue being the heat. In the X-ray range 1% of the electron beam is converted to X-rays the rest to heat. This is why X-ray tubes are either on for short periods, water cooled or have massive metal anodes.
Just a bit more than a typical microwave oven. You oven can go to about say 300 degrees celsius equivalent to about 0.05 eV.
To ionize oxygen or hydrogen (13.6 eV) by heating well that's going to take about 158,000 degrees. The long and the short of it being that ionization by heating is not easy.
I also notice the list of representatives include folk from Npower, BP, CBI and the US Embassy. Not exactly the standard sources of hardcore left wingers. Still best to gloss over these folk as focusing on them may not fit in with the promotion of FUD.
Clearly a generally pro science network supporting the scientific consensus is an important tale that absolutely warrants such a massively informed debate.
I would imagine it would be far far easier to breed (or use GM techniques) to make a crop plant that can deal with what is effectively a super short season than to attempt to light up the night. You could even store some of the daytime heat and smooth the "seasonal" temp transitions using a high heat capacity plastic mixed into the soil.
Given tundra based trees survive months with no usable light due to thick snow cover and natural summer annuals often only get light for growth for a few weeks a year this doesn't seem the biggest issue with moon farming.
Maybe try googling " lifetime risk car accident america" and reading the very first link:
http://www.medicine.ox.ac.uk/bandolier/booth/Risk/trasnsportpop.html
They give annual US odds at 1:~6200 and lifetime odds of 1:~80.
*sighs*
Okay "very bad" -> "far below average".
The main advantage of computer driven cars is that they learn faster than humans. A human is at a massive learning disadvantage as he can't exactly replicate his actions, recall his sensory input perfectly, vary aspects of his driving without affecting other aspects nor make changes that are smaller than his biologically imposed resolution limit. The computer can learn more from every previous race and try more things in the search for lower lap times. After sufficient versions/updates (and assuming a sporting governing body doesn't implement blocking rules) the AI's ability will exceed the upper limit imposed by the biology of the driver.
I can't see any other way this could possible work out.
So you think that lethal accidents are caused by a minority of very bad drivers. Very bad as in not mere speeding or not paying attention as almost everyone does occasionally. That would be interesting if true. Do you have any stats. or links to back that up?
I would (perhaps naively) have assumed that most types of non trivial road accidents have a chance of lethality. So I wouldn't expect those involved in lethal accidents to have a significantly different ability distribution to normal accidents.
Damn straight, why worry about the safety of yourself or others when you can be having fun.
For Americans death by car accident is about a 1 in 100 lifetime chance not massive but hardly minuscule. If you could say half that is that not a reasonable thing to do.
Thou of course everyone is an above average driver so the odds don't apply to them.
messed up the figures there it should be 0.00001% instead of 0.01%
I once mentioned shielding to a X-ray laser physicist who was talking about his high energy X-ray laser. "Aren't you worried about shielding?". The reply "O no our X-rays don't go that far in air."
That's when I realized that laser physicists have a slightly different interpretation of high-energy than most radiation physicists. I only consider high energy X-rays those at 100 keV+.
Sort of killing the buzz here but if you read the paper and maybe look at figure 2B you will see why this technique (high-harmonic generation) cannot be extended to be usable at higher keV beam without the laws of physics changing. At the current higher end their efficiency has fell to what 0.01% and falling fast.
Yes but they also fight over here. Just look at the German Motorola Vs Apple war.
I don't see how you can blame Google for an Apple led consortium giving a load of their patents to a massive patent troll (after promising to license them reasonably). You can blame Google and Intel for pushing up the price that's about it.
It would surprise me and most Atomic physicists. The exact made up of weapon components is secret but the interactions of X-rays with matter, even hot dense matter is not and such experiments are well within the domain of even an average university lab.
It's too small to be useful in tradition lens applications. Even at lower X-ray/Gamma energies when the refractive index is much bigger ( see: http://henke.lbl.gov/optical_constants/getdb2.html) you can't really use make reasonable lens.
It would be far far easier to increase the "commonly" available divergent sources' intensity than attempt to recover losses due to divergence with such a weakly focusing system. Hell, you could likely achieve a much bigger intensity increase by moving the source closer.
Can anyone even think of the medical imaging system they are envisaging. I assume they mean a phase-contrast approach but that needs a intense 700kV source with a small spot size and thin structured grating that absorb 700kV photons (which I don't think exist thou it's maybe just about within the capacity of man to make them).
The only application I can think of for this is for X-ray telescopes and astrophysics where you can't increase the source but you can have massively long imaging systems. However I will bet that their are not many interesting astrophysical events that emit only 700kV+ photons and the attenuation of the massive silicon lens may well counteract the benefit of the focusing.
The immediate never mind long term carcinogenic effect of very low dose radiation is not settled either way even in the simple case of cells. You can trudge through the related links and responses to them at :
:-)
http://en.wikipedia.org/wiki/Radiation_hormesis
if you want to bore yourself.
The problem is it's very difficult to detect the difference between a small negative effect and a similarly sized positive one. Plus due to complicating effects like the bystander one it is likely that the pattern, flux and nature of the applied radiation will complicate the results.
At such low radiation levels in more complex organisms to know for certain you would need to have an unethical massive experiment using millions of animals with half being irradiated in a precisely controlled way. Rightly so this doesn't happen and so researchers have to look at smaller samples often with massive variations between them. Which is why the issue is not settled.
O and all radiation isn't bad, look at radiotherapy
Couldn't agree more on the terminology. Eg phase-shift,interference,diffraction,scattering all used to describe similar things in different fields. :-) But thats for another board.
Yes I did wonder about double slit experiments (started in Atomic physics) but more so about the pattern's mere existence for single photons. The question of its shape seems trivial by comparison.
Okay sorry my mistake I thought you meant a direct phase measurement.
IMHO they are exactly doing a classic optic phase-constrast technique. Not exactly the same geometry as in microscopes due to the vastly superior optical beam available. But very similar and identical to the one often used for accelators X-ray CT which is why they reference this research. If you think this is wrong thats fine, I just disagree.
Ah okay, I understand what you mean now. However I still think your wrong as whilst you can measure phase of photons in the RF/Microwave domain there is no method of measuring phase directly with optical photons never mind 100keV electrons.
Indirectly by observing the imaging pattern (like a classic optical fringe pattern) the phase-shift can be done. Thou you might have to manipulate the beams to make the pattern more obvious as in classic interferometers or classic phase-contrast microscopy. Or you can look from "far" enough away so that the scattering from the phase-shift is enough to produce an image from which you can infer the phase-shift itself. This is the technique the Sheffield electron folk, some telescope folk and the X-ray folk can use. There is actually a smooth continuum of techniques depending on how far away your detector is, now transparent you object is and now you block or deal with the transmission image that "contaminates" the pure scatter/phase-shift image. But lets ignore the other fields for now as this is a semantic debate.
In this particular case they are not measuring the phase of the electron wave. They use a Gatan, Inc. ORIUS SC200 CCD Camera. Such a detector doesn't even detect the electrons directly. Instead it detects the 10 or so optical photons emitted from the scintillator placed in front of a CCD when each electron strikes it (the optical photons are of course emitted with random phase). So all they can possibly detect is an electron intensity profile. As this is a far field diffraction pattern you can mathematically reconstruct the sample that would produce it.
They themselves point on page 2 left column that this technique has been about for 40 years in the optical world and admit X-ray researchers have looked into it before.
I have done optical super resolution microscopy myself but have never heard about the MRI equivalent. Then again I don't really know much about MRI research so that's not so surprising and I obviously defer to your knowledge on this. Similarly I have seen synthetic aperture talks but only those done with Ultra sound or telescope based data.
Interesting now all the very different imaging modalities have vastly different implementation rates for similar techniques. Whilst the method and technology of acquisition is responsible for some of this I suspect a lot of it is researchers simply not knowing what is going on in other fields. (As I myself demonstrate with MRI)
Okay take your point on the MRI. I'd describe that as phase encoding spatial information rather than interference but I accept your way is just as valid. It's certainly not the most common method in X-ray phase-constrast CT. However this method is used for X-ray CT at synchrotrons.
That's not true. When a physicist (like me) talks about an interferometer generally we mean a device that can measure phase shift or relative phase by comparing a beam with unknown phase to a separate known phase-shift reference beam.
See: http://en.wikipedia.org/wiki/Interferometry
Such interferometers (which normally use a point detector and therefore aren't measuring a pattern) have been about for well over a hundred years
See: A. Michelson, E. Morley. American Journal of Science: 333–345. (1887). So I simply don't know what you mean by "traditionally done".
Inferring phase-shifts from diffraction patterns is different (but obviously mathematically related) and more limited. For example a light beam going normally through a thin sheet of glass has no diffraction pattern. However it has a measurable phase-shift with an optical interferometer.
When you say we can only recently measure phase at high frequency for light I think I am missing something. If you are clever with the optics you can make all phase-shifts manifest as intensity variations. This is exactly the principle of a phase-contrast optical microscope widely available since the 60s.
Saying you don't need a lens is just wrong. At the very very least you need a lens to focus the beam onto the specimen.
O and if you actually read the paper you'll see that on the right hand column of page 5 all the current experimental limitations on resolution are listed. That the lens doesn't feature doesn't mean it follows that it is just down to wavelength, it's not. There is no lens in any hospital X-ray systems and your 100 keV diagnostic X-rays does not give you ~0.01nm resolution images. There is a world of difference between physics based resolution limits and that which can actually be obtained in most cases.
The method is nice, worthy of a nature paper and will improve on the future. However those that are saying that this is it "they got this" for imaging are just plain wrong. It's a new imaging modality we get one every couple of years or a few a year depending on your definition.
nMR measures the spectrum of RF emitted when nuclei excited into alignment by resonant RF pulses relax out of alignment with an externally applied magnetic field. MRI which is the correct name for the imaging modality measures the pattern of this RF emission. Maybe I am missing something but now exactly is this an interferometric process?
As to how this IS used in a research CT scanners google "phase-constrast CT". O and you want to do this in future to reduce patient dose or highlight soft-tissue boundaries which aren't obvious on a standard CT.