05-01-2014, 03:01 AM
This is going to be pretty long, but first I have to set up some things. I need to make sure I am explaining it to the depth and level to make my point.
According to their website, they are using “airborne imaging spectroscopy” for multispectral remote sensing. They supposedly use satellites currently in orbit to do this imaging.
Let's look at this. From an analytical instrument standpoint, the term “spectroscopy” means that you are using wavelengths in the electromagnetic spectrum, whether it is gamma rays, microwaves, ultraviolet rays, visible wavelengths, infrared, or whatever. I'll call this region of the electromagnetic spectrum the satellite utilizes just “radiation” because I don't know what the region really is. This kind of analysis really is long-range spectroscopy: the atoms of the elements being looked for (the analytes) have to interact WITH the radiation in question, and then the sensor can read the change, either absorption or emission, of the radiation.
An example of this would be UV/Vis (ultraviolet/visible) spectroscopy. A sample is placed in line with a beam of light, either in the ultraviolet or visible range (or both) and the absorption of the light is determined from the amount of light that is detected after going through the sample. The light is absorbed by the molecules of the analyte and this energy is dissipated in some manner by the sample. We typically will see that the energy is absorbed at certain wavelengths, but not at others, and it is from these tell-tale spectra we can make a determination as to what the sample MAY be. The spectra may not be specific enough to make a definitive determination, but it is a start.
What if the analyte doesn't respond to the radiation? It can't be detected. It is as simple as that.
How close does the radiation have to come to the analyte? It has to interact with it, so pretty damn close. How close does the detector have to come to the analyte? That depends on the nature of the testing being done. Spectroscopy as noted above can be done at a pretty far distance.
So far, so good. Now for the rest of it. They claim they use these technologies:
1. Earth Remote Sensing: This I'll believe, but only to a certain point. If remote sensing was able to get you information about where oil and gas reserves are located, then the drilling companies wouldn't have any excuse to come up dry would they? All these companies involved with prospecting for oil/gas/minerals/what-have-you would be using them, wouldn't they?
2. Multispectral imaging: again, so far so good. See above.
3. Gamma radiation: ditto. This should be good as well. All of these are easily attained by what they first claim they are using.
4. Radiation chemistry. Whoa. For them to use this, they have to be a lot closer than several thousand meters to the analyte (or object). There are three kinds of radiation used in “radiation chemistry:” alpha, beta, and gamma. Alpha and beta particles are easily blocked. A sheet of paper can do it for alpha, and clothing is usually considered good for beta. Gamma rays require the lead shields, six feet of earth, that kind of thing. So for a remote standpoint, only gamma rays would be applicable. Most people using “radiation chemistry” use alpha/beta emitters in trace amounts to determine such things as mechanisms of chemical reactions or where specific antibodies/antigens/drugs or whatever are taken up in living systems or metabolic byproducts from the administration of the compound. So, this one seems to amount to #3 above. Uh...right. Uh...no.
5. NMR spectroscopy. REALLY!!!???? Nuclear magnetic resonance spectroscopy depends on the spin of the nuclei of the elemental isotope being examined. Some isotopes will have integral spins, and some will have fractional spins. Some isotopes have no spin at all. If we look at elements with spin of 1/2, we will find that when the element is in the presence of an external magnetic field, two spin states will exist: +1/2 and –1/2: They spin in opposite directions, but the energy related to the two spins is not the same. The -1/2 state is higher in energy than the +1/2 state. Thus is a difference in energy associated with the two spin states, and the amount of the difference depends on the strength of the external magnetic field: the stronger the magnetic field, the greater the difference in energy. For NMR spectroscopy to be viable, the analyte must first have a spin, and secondly it must be subjected to strong magnetic fields.
The earth's magnetic field is not constant, but is approximately 0.0001 T (tesla) at ground level. Modern NMR spectrometers use magnetic fields of 1 to 20 T, and typically get a difference in energy between the two spins of less than 0.1 cal/mol. [“cal” here is calorie, a unit of energy, and is 0.0001 Calories, meaning the kind you measure for your food intake. One thousand calories (chemical energy) is one Calorie (food energy). A “mol” is a mole of a substance, 6.022 times 10 to the power of 23 (6.022 x 10^23) atoms of the substance. A mole is just a number, like a dozen is a number. If you want to know the mass of a mole of a substance, look on a periodic table. A mole of aluminum weighs 26.98 grams; a mole of titanium has a mass of 47.87 grams.]
Now that we have set this up, the fun can start. You hit the analyte with radio frequency (rf) energy at right angles to the magnetic field. If rf energy corresponds EXACTLY to the energy difference in the spin state separation of given set of nuclei, the nuclei will excite from the lower +1/2 state to the higher -1/2 state. For elements with spin 1/2, the difference between these two states at a given magnetic field strength is proportional to their magnetic moments, and thus the NMR instrument will have to be tuned to the specific elements being investigated. To give you a perspective of how many nuclei we are talking about, at room temperature the two states are nearly equally populated. In a magnetic field of 2.34 T the excess population in the lower energy state is only six nuclei per million nuclei present. Even at this small numbers, it is enough to measure.
However, this jump to the higher energy state is unsustainable over the long term, and the nuclei will relax back down to their previous energy states, giving off rf energy. This rf energy can be easily absorbed (as it is weak indeed) and thus the detector must be close to the sample. If radio waves were not affected by atmospheric conditions or by water, then it wouldn't attenuate so badly with distance and obstructions! The range of frequencies used fall within the radio/television region of the electromagnetic spectrum, and I don't think that the FCC would allow a company to use strong sources of such at great distances. Too much rf energy and you get saturation at the higher spin state and useful signals disappear. Too little rf energy and you get no flip.
Another complication is the temperature of the sample: the molecules in contact with the sample can induce local fluctuating electromagnetic fields that possibly match the frequency of the nucleus being studied. This is necessary, since the spinning nucleus does not spontaneously change its spin state without something nudging it. The efficiency of this mechanism depends on temperature and viscosity of the solution, and thus, NMR spectroscopy is normally done in the liquid phase, either as a solution or as a neat solution. This is not the only mechanism involved in relaxation, but I won't get into it here. The upshot here is that the deeper you go the colder and more viscous the water, and thus the relaxation time can change. Longer relaxation times are less efficient, and thus the signals become weaker.
Samples submitted for NMR analysis are typically small and put in sealed glass tubes. The sample itself is spun to average any magnetic field variations and also to average any aberrant signal due to any imperfections in the tube. The tube is placed between the poles of two powerful magnets. The rf pulse is delivered, and the relaxation emission signal is monitored by a receiver coil that surrounds the sample. You can vary the magnetic field over a small range while observing the rf emitted, or vary the rf pulse within a fixed magnetic field and observe the rf emitted.
High resolution continuous wave (CW) NMR takes time, (as much as 10 minutes or more) as it takes a while to sweep the region of interest. Conditions MUST remain constant during this entire time.
Lower resolution NMR can be faster: you it it with a very short relatively strong burst of rf energy to excite all the nuclei simultaneously, and it takes just a few seconds. However, you get overlapping relaxation signals because each nuclei will emit as it relaxes. Such signals are analyzed using Fourier transform mathematical analysis, and it is repeated three times and the results are combined.
High resolution NMR is not feasible on copper, as the peaks are too broad and the energy shift too wide. For nickel, NMR may not be feasible at all; it appears that it depends on the nickel complex being studied. Paramagnetic NMR is apparently possible, but resolution and detail is not there. It will take a LOT more scans to get it (10,000 anyone?), and the sweep window will have to be correspondingly enlarged.
There is such a thing as solid state NMR, but it appears that the line broadening is worse with it than you would see with liquid NMR.
Somehow, long-distance NMR just doesn't seem feasible to me.
6. The last “technology” is proprietary know-how. Let's wave the hands and proclaim ourselves to be experts, but we can't tell you because it's proprietary. If we told you, it's assimilation or death. Maybe. And anyone stating that he cannot tell you the technique he used to determine the result he got because it is "proprietary" is trying to pull the wool over your eyes. He doesn't have to tell me in painful detail everything about his instrumentation, but he better be able to explain it to my satisfaction. Where are his satisfied customers? I'm not seeing any.
If I'm wrong, tell me. I can always learn something new. NMR was not my specialty in graduate school, but as it was on the curriculum, I had to learn it.
My take on this guy? Run away. Run far away.
Diana
According to their website, they are using “airborne imaging spectroscopy” for multispectral remote sensing. They supposedly use satellites currently in orbit to do this imaging.
Let's look at this. From an analytical instrument standpoint, the term “spectroscopy” means that you are using wavelengths in the electromagnetic spectrum, whether it is gamma rays, microwaves, ultraviolet rays, visible wavelengths, infrared, or whatever. I'll call this region of the electromagnetic spectrum the satellite utilizes just “radiation” because I don't know what the region really is. This kind of analysis really is long-range spectroscopy: the atoms of the elements being looked for (the analytes) have to interact WITH the radiation in question, and then the sensor can read the change, either absorption or emission, of the radiation.
An example of this would be UV/Vis (ultraviolet/visible) spectroscopy. A sample is placed in line with a beam of light, either in the ultraviolet or visible range (or both) and the absorption of the light is determined from the amount of light that is detected after going through the sample. The light is absorbed by the molecules of the analyte and this energy is dissipated in some manner by the sample. We typically will see that the energy is absorbed at certain wavelengths, but not at others, and it is from these tell-tale spectra we can make a determination as to what the sample MAY be. The spectra may not be specific enough to make a definitive determination, but it is a start.
What if the analyte doesn't respond to the radiation? It can't be detected. It is as simple as that.
How close does the radiation have to come to the analyte? It has to interact with it, so pretty damn close. How close does the detector have to come to the analyte? That depends on the nature of the testing being done. Spectroscopy as noted above can be done at a pretty far distance.
So far, so good. Now for the rest of it. They claim they use these technologies:
1. Earth Remote Sensing: This I'll believe, but only to a certain point. If remote sensing was able to get you information about where oil and gas reserves are located, then the drilling companies wouldn't have any excuse to come up dry would they? All these companies involved with prospecting for oil/gas/minerals/what-have-you would be using them, wouldn't they?
2. Multispectral imaging: again, so far so good. See above.
3. Gamma radiation: ditto. This should be good as well. All of these are easily attained by what they first claim they are using.
4. Radiation chemistry. Whoa. For them to use this, they have to be a lot closer than several thousand meters to the analyte (or object). There are three kinds of radiation used in “radiation chemistry:” alpha, beta, and gamma. Alpha and beta particles are easily blocked. A sheet of paper can do it for alpha, and clothing is usually considered good for beta. Gamma rays require the lead shields, six feet of earth, that kind of thing. So for a remote standpoint, only gamma rays would be applicable. Most people using “radiation chemistry” use alpha/beta emitters in trace amounts to determine such things as mechanisms of chemical reactions or where specific antibodies/antigens/drugs or whatever are taken up in living systems or metabolic byproducts from the administration of the compound. So, this one seems to amount to #3 above. Uh...right. Uh...no.
5. NMR spectroscopy. REALLY!!!???? Nuclear magnetic resonance spectroscopy depends on the spin of the nuclei of the elemental isotope being examined. Some isotopes will have integral spins, and some will have fractional spins. Some isotopes have no spin at all. If we look at elements with spin of 1/2, we will find that when the element is in the presence of an external magnetic field, two spin states will exist: +1/2 and –1/2: They spin in opposite directions, but the energy related to the two spins is not the same. The -1/2 state is higher in energy than the +1/2 state. Thus is a difference in energy associated with the two spin states, and the amount of the difference depends on the strength of the external magnetic field: the stronger the magnetic field, the greater the difference in energy. For NMR spectroscopy to be viable, the analyte must first have a spin, and secondly it must be subjected to strong magnetic fields.
The earth's magnetic field is not constant, but is approximately 0.0001 T (tesla) at ground level. Modern NMR spectrometers use magnetic fields of 1 to 20 T, and typically get a difference in energy between the two spins of less than 0.1 cal/mol. [“cal” here is calorie, a unit of energy, and is 0.0001 Calories, meaning the kind you measure for your food intake. One thousand calories (chemical energy) is one Calorie (food energy). A “mol” is a mole of a substance, 6.022 times 10 to the power of 23 (6.022 x 10^23) atoms of the substance. A mole is just a number, like a dozen is a number. If you want to know the mass of a mole of a substance, look on a periodic table. A mole of aluminum weighs 26.98 grams; a mole of titanium has a mass of 47.87 grams.]
Now that we have set this up, the fun can start. You hit the analyte with radio frequency (rf) energy at right angles to the magnetic field. If rf energy corresponds EXACTLY to the energy difference in the spin state separation of given set of nuclei, the nuclei will excite from the lower +1/2 state to the higher -1/2 state. For elements with spin 1/2, the difference between these two states at a given magnetic field strength is proportional to their magnetic moments, and thus the NMR instrument will have to be tuned to the specific elements being investigated. To give you a perspective of how many nuclei we are talking about, at room temperature the two states are nearly equally populated. In a magnetic field of 2.34 T the excess population in the lower energy state is only six nuclei per million nuclei present. Even at this small numbers, it is enough to measure.
However, this jump to the higher energy state is unsustainable over the long term, and the nuclei will relax back down to their previous energy states, giving off rf energy. This rf energy can be easily absorbed (as it is weak indeed) and thus the detector must be close to the sample. If radio waves were not affected by atmospheric conditions or by water, then it wouldn't attenuate so badly with distance and obstructions! The range of frequencies used fall within the radio/television region of the electromagnetic spectrum, and I don't think that the FCC would allow a company to use strong sources of such at great distances. Too much rf energy and you get saturation at the higher spin state and useful signals disappear. Too little rf energy and you get no flip.
Another complication is the temperature of the sample: the molecules in contact with the sample can induce local fluctuating electromagnetic fields that possibly match the frequency of the nucleus being studied. This is necessary, since the spinning nucleus does not spontaneously change its spin state without something nudging it. The efficiency of this mechanism depends on temperature and viscosity of the solution, and thus, NMR spectroscopy is normally done in the liquid phase, either as a solution or as a neat solution. This is not the only mechanism involved in relaxation, but I won't get into it here. The upshot here is that the deeper you go the colder and more viscous the water, and thus the relaxation time can change. Longer relaxation times are less efficient, and thus the signals become weaker.
Samples submitted for NMR analysis are typically small and put in sealed glass tubes. The sample itself is spun to average any magnetic field variations and also to average any aberrant signal due to any imperfections in the tube. The tube is placed between the poles of two powerful magnets. The rf pulse is delivered, and the relaxation emission signal is monitored by a receiver coil that surrounds the sample. You can vary the magnetic field over a small range while observing the rf emitted, or vary the rf pulse within a fixed magnetic field and observe the rf emitted.
High resolution continuous wave (CW) NMR takes time, (as much as 10 minutes or more) as it takes a while to sweep the region of interest. Conditions MUST remain constant during this entire time.
Lower resolution NMR can be faster: you it it with a very short relatively strong burst of rf energy to excite all the nuclei simultaneously, and it takes just a few seconds. However, you get overlapping relaxation signals because each nuclei will emit as it relaxes. Such signals are analyzed using Fourier transform mathematical analysis, and it is repeated three times and the results are combined.
High resolution NMR is not feasible on copper, as the peaks are too broad and the energy shift too wide. For nickel, NMR may not be feasible at all; it appears that it depends on the nickel complex being studied. Paramagnetic NMR is apparently possible, but resolution and detail is not there. It will take a LOT more scans to get it (10,000 anyone?), and the sweep window will have to be correspondingly enlarged.
There is such a thing as solid state NMR, but it appears that the line broadening is worse with it than you would see with liquid NMR.
Somehow, long-distance NMR just doesn't seem feasible to me.
6. The last “technology” is proprietary know-how. Let's wave the hands and proclaim ourselves to be experts, but we can't tell you because it's proprietary. If we told you, it's assimilation or death. Maybe. And anyone stating that he cannot tell you the technique he used to determine the result he got because it is "proprietary" is trying to pull the wool over your eyes. He doesn't have to tell me in painful detail everything about his instrumentation, but he better be able to explain it to my satisfaction. Where are his satisfied customers? I'm not seeing any.
If I'm wrong, tell me. I can always learn something new. NMR was not my specialty in graduate school, but as it was on the curriculum, I had to learn it.
My take on this guy? Run away. Run far away.
Diana
