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Hi, original AC here.

Active systems, as they exist now, are portal only. Thus there is only the exposure to several seconds of either millimeter-wave or x-ray radiation while in the portal. Also, the operators have no control over the emitted power. It is constant, person to person. The SNR of active systems is incredible even at such low radiation levels; increasing it would do nothing useful.

Regarding your comment of crowd scanning; this is how some passive systems work, but (currently) no active systems. Passive, i.e., picture a CCD. Visible or IR currently, right? Well, imagine a millimeter-wave/terahertz one. Still passive, but can see through clothing at decreased spatial resolution (diffraction limited). No harm done by standing in front of a passive sensor all day long.

About the transmission/storage of images: That is determined by the final system manufacturer and the TSA. I work only on the imaging hardware and initial display. I tend to agree with you, however.

Why millimeter-wave over IR? IR cannot penetrate clothing as well as you think. And IR sensors are no more 'safe' than passive millimeter-wave/terahertz sensors: both are 100% safe.

Hi, original AC here.

It's not IR... IR cannot penetrate clothing, so it is not great for this application; here's the paper you want to read. As I said, the image in the NG article is in the approximately 100-2000 GHz range, and it's passive.

And yes, everyone is confused about the sensor modalities. There are three. 1) Active narrowband millimeter-wave. Basically imaging radar. 2) Passive broadband millimeter-wave/terahertz. 3) X-ray backscatter. (also active of course, but a stretch to be called radar)

Each one has advantages and disadvantages. The problem is that they all get lumped into the "body scanner" category in the popular press (since that is what they do), and then the advantages and disadvantages get completely mixed up. To answer your question, the TSA is currently using (1) and (3) in airports.

Regarding the "strip search" issue, it really seems to depend on the individual. Yes, the high-resolution systems essentially display you without clothing, but on the other hand, the images look nothing like what you would see with your eyes. It has been said that they could appear on the front cover of Time or Reader's Digest in grocery store checkout lanes, and they wouldn't get covered up like the cover of Cosmo usually does. That's just someone's opinion, of course. Everyone has them...

Perhaps it's time to once again point out that "scientific proof" is a red herring.

Even after Quantum Mechanics and Einstein's Theory of Invariance, Newton's Laws of Motion and Kepler's Law of Planetary Orbits apply fully to all the conditions on which they were first based. No planet travels close enough to light speed for relativity to invalidate those theories as they apply to the observations on which they were based. These 20th century discoveries are often trumpeted in light reading for non-scientists, and some lower quality textbooks, as "overturning" classical mechanics or the like, but in fact they only extended what was previously known and proven, with modifications that really only apply to entirely new classes of observations. The conditions that require relativity or QM, nobody had thought they understood before that, so nothing was disproved by those extensions of human understanding.

And while LIGO searches for the wave or particle responsible for gravity, nobody suspects we might find it has a repulsive component we never noticed before, or that the value of the universal gravitational constant will be radically altered. Gravity is attractive, and its magnitude is known to a high degree of certainty, and it is the same value measured hundreds of years ago for most scenarios in which we calculate gravity. So I am not discounting the occasional dramatic leap in the expansion of knowledge in any way, but it is false of you to claim that in science we can never accurately use the words "prove" and "proof".

There was legitimate doubt about the ability of carbon dioxide to significantly impact global mean temperature, but there is not now, since its emission spectrum was proven to not overlap water's, by the identification of well-defined bands, rather than a blur -- in the 1950s. No legitimate scientist doubts it because it is proven beyond a shadow of reasonable doubt by things that are absolutely known about physical optics. Plenty of ignoramuses can be persuaded otherwise by overpaid charlatans, but that is not part of the scientific process. It is part of social and political processes we all ought to outgrow, post haste.

There is significant uncertainty in all of these areas. And based on all that uncertainty, it is impossible to draw hard conclusions about which way this plays out.

Or do you rely, to make your rhetorical points, on a less exact definition of "significant" than is required of a scientist, to use the same word about a research subject? Scientists really are held by their profession to higher standards than the carbon industry spokespersons who are the scientists' opponents in the public "debate" about climate and related policy. Policy itself is a proper subject of debate, but science is not, and yet here we are, debating the facts themselves, not only the policies we should adopt to deal with the facts. Coal and petroleum corporations have countered the best science with scientifically unsupported, factually incorrect talking points, and for decades they have been very successful in that little game. And now, data thieves' motives are being assumed as pure as the driven snow and their "findings" taken at face value, parroted without analysis by the leading "news" sources, who have made no effort to ascertain who the data thieves are, what their motives were, and which petroleum and coal corporations paid them to do their heist (obvious motive, basic journalistic integrity requires trying to find the answer to such an obvious question), before treating the thieves with ultimate credulity, and in the process baselessly impugning the life's work of dozens of scientists directly, and thousands more implicitly.

My thesis is that such corporatist "success" (cheating, really, which is a very different thing from bona fide success, thus the "sarcastic quote marks") is directly the result of the professional constraint by which scientists are not permitted to just say a thing is "significant," but must quantify any significance we assert, at the risk of our careers. Scientists work by the most exacting rules of any profession in the world, while corporate-sponsored opponents play around, virtually no-holds-barred. Your comment about a "foregone conclusion" is particularly ironic in this context, because everybody knows that the most profitable spin is always the foregone conclusion for which any corporation will pay. If something similar is true of even one climate scientist whose work has helped prove The Carbon Dioxide Greenhouse Effect, the burden of proof has yet to be met. Even once. That is significant, statistically! Zero out of all climate scientists have been proven corrupt. Saying mean things about others and being frustrated when one's hypothesis is found to need further refinement is not scientific malpractice, it's just human, and that's the worst that the stolen University of East Anglia files show.

So before I refute, with scientific research results in the public domain, each of your five assertions of global uncertainty ("nobody knows" as opposed to you don't know) about specific relevant facts of global warming and related policy, I am just asking you to quantify how much uncertainty you assert that there is in the leading science. Alternatively, you could admit that your own uncertainty is specific to you and at least to some degree commensurate to your personal ignorance of the relevant facts, and therefore not necessarily indicative of what full-time professional climatologists do or don't know and with what certainty it is known, and can be known to diligent voters. I don't ask you to agree immediately that everything predicted by current coupled ocean-atmospheric global circulation models is a 100% accurate forecast, only to recognize that what you don't know is not neces

"No scientist would ever - ever - delete raw data, at least without a gun to his or her head."

Cough. The NASA Apollo tapes? The ones found under a staircase in Australia with a sign saying "beware of the leopard"?

After about Apollo 14 it seems even the scientists were bored with the whole moon landing thing.

Also Princeton apparently doesn't keep very good historical records either.

"You'd think somebody must be writing a history of the Institute. You'd think there would be some records of what the seminars were, but I'm told that as far as records go, the records of our physics here at the university are in a shambles. The wastebasket is full of stuff at the place up on Nassau Street where the university archives are. So if somebody following up the lead of this morning's paper decides to shred all of those, there will be no earthquake that I know of. I don't know anybody who's working with those papers or organizing them."
-- John Wheeler, oral interview, 1994. http://www.aip.org/history/ohilist/5908_9.html

I have this impression of scientists as a bunch of ADD eight-year olds hopped up on lemonade. That's historical data! Don't care about that! Only old people like the past! Onto something newer and cooler now! Grant monies kthx!

Unfair I know, but sheesh. Forgetting how we got the science we have bugs me. Sometimes going back and re-analysing old raw data with a new methodology can lead to very different conclusions, and sometimes the people running the labs at the time weren't all squeaky clean saint-geniuses. Even in the 'hard' sciences like physics, especially post WW2 with all the atomic secrecy and government money. Wheeler elsewhere in that interview series observes that even all the scientists working on the H-bomb and fusion didn't know what each other were doing, and some still can't talk until their classification expires. So reanalysis of old data in the light of new knowledge can be very very important.

We're salvaging historical data in the arts. The BBC purged old Doctor Who tapes, and most of the tapes of Metropolis the movie were lost but one was recently found. Jason Scott at http://www.textfiles.com/ is salvaging 1980s computer history. So we should be pushing for the same level of data preservation in science.

The role of CO2 in warming the earth was first worked out by Arrhenius in the 1900's. A nice summary of the development of scientific thought regarding CO2 and climate modeling can be found here

I think the bigger problem with climate change science is that it is SOOO hard to get definitive answers. For example, look at this essay on rapid climate change. I think today most people believe that rapid(less than 100 year) climate shifts are possible and have happened, but the data isn't bulletproof and until recently(last 20 years) the majority probably wouldn't have believed it was possible. Separating the crap from the stuff that is probably-correct is too difficult for any layperson. I'm convinced that the world is probably rising in temperature from human-caused CO2/methane, but what effects that will have are unclear to me. Right now, it looks like the ocean can only rise a couple cm/100 years(a.k.a. undetectable compared to the tide).

I think deforestation and overpopulation are the real global issues for the next 100 years. The human population is still growing very fast and we have cut down most of the forests in the world. Something drastic has to happen in the next 100 years on both of these issues.

Competitive technologies are available. Here's a commercial small, low-cost neutron monitor. That uses zinc sulfide with boron. Boron detectors seem to be gaining on helium-3 detectors. What seems to have happened is that Homeland Security locked onto a specific detector technology and supplier, and now the supplier has problems. This is a bureaucracy problem, not a technology problem.

The basic physics experiment is called a Reuben's Tube. Build one with only a single orifice at a high-pressure resonance point, install a check valve, and collect the pressurized gas in a tank. Here's another concept.

I thought these guys had it pegged?

Carbon nanotubes, with a tensile strength of up to 100 GPa, are the strongest material ever discovered [10]. To exploit this superior property for practical applications, individual carbon nanotubes have been assembled into macroscopic fibers [11,12]. However, these macrofibers show a very low tensile strength of less than 3.3 GPa [12 15]. This is mainly due to the clustering of nanotube ends, internanotube slippage and intrananotube defects. In contrast, the CCTs have demonstrated much improved mechanical properties compared to carbon nanotube fibers of similar sizes. Figure 4(a) shows the maximum tensile strength of 6:9 GPa of a CCT.
....
The CCTs synthesized here have a unique architecture with rectangular macropores across the tube walls and layered crystal structures in the solid walls. This unique architecture renders them a combination of superior prop- erties, including ultralight weight, extremely high strength, excellent ductility, and high conductivity. These unique architectural and physical properties give them great po- tentials for a variety of advanced applications. For ex- ample, the diameter and the length of CCTs are com- parable to those cotton fibers and the tenacity of the CCTs is 224 times that of cotton fibers. This suggests that conventional textile technologies can be used to make CCT fabrics that are much stronger than any current fabrics for applications such as body armors and light- weight, high strength composite structures. Other potential applications include making in situ self-healing composite structures, medical devices to deliver/release multiple drugs simultaneously, and microelectromechanic al sys- tems, to name only a few.

Of course, producing enough of the stuff and making the belt out of it is still non-trivial...

I checked out the pdf of the paper, and didn't see any numerical limit stated, just equations.

That's because the linked PRL paper in the article summary is incorrect. It is two years old, not "published today" like TFA states. The actual PRL paper, published today, can be found right here.

You're way out of my league on this one, but if I had to guess I'd say that any alteration to an observable property will have a similar effect on the particle as observing the spin. Check the Wikipedia article on quantum entanglement.

Also, you can (probably) get information out of a singularity. See here.

See Taking Cosmic Rays for a Spin (2006). Also a very informative section in Spencer Weart's Discovery of Global Warming.

The TOTAL confinement time looks like it'll be measured in microseconds at most on this thing, no way is there time for active control of the plasma during a shot like that.

I see that. So what do they want all the compute power for? I'd assumed I was reading an oversimplified version, and all the compute power was to actively stabilize something. If they just need a simultaneous push, they don't need compute power. I'm missing something.

There's work on active stabilization. See "Active-Feedback Control of the Magnetic Boundary for Magnetohydrodynamic Stabilization of a Fusion Plasma". That's a 2006 paper on a scheme involving 192 active feedback coils to stabilize a plasma. There's other work like that, and hope that one of the designs that's almost stable might be nudged into stability with active control.

How on earth did your post get modded as Informative? You link to a site that says "The Sun's energy output has not increased since direct measurements began in 1978'. That is completely untrue, the sun's energy output varies daily, and the sun goes through 11 year cycles in which it's overall output increases or decreases. Try this article. Or this one. Or just google it yourself!. In fact, one of the articles you link to disputes the other! Maybe you should try reading a few other sources than New Scientist, as there are mountains of evidence that would suggest the science isn't as nearly as conclusive as the IPCC backers would like you to believe.

Conventional thin-film photovoltaics rely on the optical generation and separation of electron-hole pairs (EHPs) with an internal electric field, as shown in Fig. 1a. Among different factors, the absorption efficiency of the material and the minority carrier lifetime often determine the energy conversion efficiency15. In this regard, simulation studies have previously shown the advantages of three-dimensional (3D) cell structures, such as those using coaxially doped vertical nanopillar arrays, in improving the photocarrier separation and collection by orthogonalizing the direction of light absorption and EHPs separation (Fig. 1b)16.

Later in the paper they discuss the light-absorbing properties of these kinds of pillar arrays:

In addition, 3D nanopillar or nanowire arrays, similar to the ones used in this work, have been demonstrated in the past to exhibit unique optical absorption properties13,18. Similarly, we have observed reduced reflectivity from CdS nanopillar arrays especially when the inter-pillar distance is small (see Supplementary Fig. S6). This observation suggests that 3D nanopillar-based cell modules can potentially improve the light absorption while enhancing the carrier collection.

References 13,18 are:
L. Tsakalakos, J. Balch, J. Fronheiser, B. A. Korevaar, O. Sulima and J. Rand "Silicon nanowire solar cells". Appl. Phys. Lett. 91, 233117 (2007). doi 10.1063/1.2821113
Hu, L. and Chen, G. "Analysis of optical absorption in silicon nanowire arrays for photovoltaic applications". Nano Lett. 7, 3249-3252 (2007). doi 10.1021/nl071018b

Quoting from that second paper:

We found that, in comparison to thin films, nanowire array based solar cells have an intrinsic antireflection effect that increases absorption in short wavelength range.

Essentially the nanowire arrays are acting as anti-reflection coatings and allowing the light to instead be absorbed.

Whereas the instability of ordinary liquid columns is driven by molecular surface tension, possible mechanisms for droplet formation in granular systems include hydrodynamic interactions with the surrounding gas, inelastic grain-grain collisions, and cohesive forces. Hydrodynamic interactions have indeed recently been associated with fluctuations in the profile of streams falling in air 9; however, from experiments across a wide range of ambient pressures down to 0.03 kPa we find that grain-gas interactions do not drive clustering (Supplementary Fig. S1), in agreement with earlier work 6.

(Emphasis added.)

For anyone curious, reference 6 is:
Mobius, M. E. Clustering instability in a freely falling granular jet. Phys. Rev. E 74, 051304 (2006). doi: 10.1103/PhysRevE.74.051304

If you don't have access to Phys. Rev. E., you can read a preprint of the same paper on ArXiv here.

That paper does measurements down to 0.03 kPa (1/5000 atmospheric pressure), and concludes:

Clustering is observed down to the lowest pressure and the presence of air leads to larger clusters but does not initiate the cluster formation.

American Journal of Physics

May 2002, Volume 70, Issue 5, pp. 558-559

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=AJPIAS000070000005000558000002&idtype=cvips&gifs=yes

Surpsingly complicated, couldn't find any simple practical answers. Sorry. I did find some nifty pictures though.

Bacteria react to injury, they remember the past, and they even predict the future. If you buy into the theory that causing pain is immoral then every cow is a walking Auschwitz. (not even to mention the problem of brushing teeth)

By the way, there is no philosophical reason why "it feels pain" is a better standard for deciding whether injuring something is cruel than any other arbitrary standard, see Hume

you refrain from pejoratives and hyperbole

Gee, thanks, "chump"! :->

I'm going to have a hard time translating something like Entropy into an equation...

The link I provided before does so, using the actual thermodynamic definitions of entropy. Here it is again (PDF paper it links to, costs money though). Even by a major overestimate of the amount of entropy in living things, the sun puts in over a trillion times more energy available to decrease entropy than all living things on Earth produce.

The main problem is that Entropy is not "disorder". The other problem is that entropy can and does decrease on Earth, all over the place... though the total entropy in the Universe does go up. If the naive understanding of entropy were correct, snowflakes couldn't form. Here's a discussion that addresses your 'broken glass' example pretty well, noting that "order" and "design" are two quite different things still. It also addresses something else you say:

I argue that what can't happen with an individual is impossible to take place within a population, because a population can always be split ad infinitum until it is a population of one.

You didn't cover semiconductors in your electrical engineering classes? They did in mine. Holes, doping, band gaps, etc. - such phenomena can't be observed in single atoms, only in collections thereof. (BTW, entirely unrelated aside: I once ran it through an anagram generator and discovered that "electrical engineering" could be rearranged to "rectilinear negligence". :-> ) What about convection? How about dipolar bonding in water - of no import in an individual molecule, but leads to anomalously high surface tension in liquid water, and the paradoxical expansion of solid vs. liquid water at Earthly temperatures and pressures?

Ponder for a moment how you'd measure the behavior of shear-thickening liquids in a single molecule. How would you make a quasicrystal out of one atom?

Early on, a blastula is composed of identical cells, but patterns of chemical reactions make "standing waves" around those cells, and start differentiation. You don't get that behavior from the individual cells - indeed, if you split those cells up, they form new blastulas, which then differentiate and develop. (One way identical twins are formed.)

Those are just the simplest examples I came up with off the top of my head. I'm going to ask a few buddies to come up with more examples of behavior seen only in populations, not individuals. It's actually a fun puzzle, thanks.

If there's a way to PM on /. please send me (geotopia) your email and we can take this offline.

Next to my name is a (slightly mangled) version of my email address. If you click on my nickname, my email's there, and you can find my home site with a "contact" page.

Or even this

This article has a good explanation of the difference between Orbital Angular Momentum and Polarization of EM waves.

If you look at the cross section of a "normal" polarized EM beam, the electric field amplitude and direction at every point of the cross section are in the same phase - although that direction may be up, down, or rotate over time depending on the polarization.

In an EM beam with orbital angular momentum, the electric field amplitude at different points on the cross section are in different phases - although it is my understanding they are usually all in the same polarization.

I suspect that the current "global warming" programs have been written with the assumption that global warming is real, and that they have built this "fact" into the programs.

Not so. Global warming results from the basic physics. Your opinions are counterfactual.

Read this blogpost explaining the models

And everyone should read this history of the science behind global warming

The lowest order state of the vortex has 4 modes because:
A) The demagnetizing field wants to minimize free magnetic poles at the surface of the element. This might be the largest contribution to the vorticity (ie. having all the spins aligned in a vortex minimizes the free poles at the surface).
B) There is a discontinuity at the center of the vortex when you look at in-plane magnetization. The spins at the center are frustrated and are forced out-of-plane.

What do you mean by "folds" on the vortex? Are you talking about impurities that would pin the field?

Don't confuse out-of-plane magnetization ("perpendicular storage") with bubble memory, they are not the same thing. (There's a reason one came much later than the other. I'd like to give you a better explanation than this, but I don't have a good reference handy. Can anyone dig something up?)

The sizes involved are indeed different, see [1] where the diameter of their elements is 700 nm, and contrast with [2] (bubble memory) where a 2x2um cell was used. Perhaps with larger circular elements you won't have a single-domain state (ie. no vortex).

... and please don't misunderstand me, I don't mean to start a flamewar. I wouldn't mind having a definitive answer to these questions too. If you can dig up any relevant papers or sources, I'd be interested to take a look at them. Thanks!

[1] http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APPLAB000079000019003113000001&idtype=cvips&gifs=yes
[2] http://www.sciencemag.org/cgi/content/abstract/246/4936/1400

What's wrong, are you mad at them because they're making you pay the actual price of your polluting products (i.e. the cost of the item AND the cost of the damage caused by the pollutants from using it)?

How is the cost (in dollar figures) of the damage calculated? Is it based on real-world cleanup costs? For the case we're talking about, electricity usage, it seems impossible to calculate because the central tax body doesn't know where I get my electricity from.

Also, environmentalists tend to count this cost many times. When a power plant is built, they want to count the hidden costs. Then when we use inefficient light bulbs, they want to count the hidden costs again!

For example, according to this article, users of electricity from nuclear power plants have paid $14.8 billion into a fund to manage nuclear waste, as of 2007. So it's at least partially paid for. (I have no idea if that's enough to cover it all.) How much do you want to bet that in a typical argument over the "true" cost of nuclear power, environmentalists will conveniently bring up the specter of nuclear waste as one of those hidden costs that need to be accounted for by taxing plasma TVs and high wattage light bulbs?

The most logical thing would be to calculate the future cleanup cost, since in reality no cleanup of any worthwhile scale is going on now. If we assume technology will advance to the point where cleanup costs are small, then it's not fair to have a large tax for it now. If we assume technology won't advance to that point, then we at least need a real estimate based on the foreseeable end of *current* technology.

Look at nuclear waste again. Right now you might say the cleanup cost is very high because the waste needs to be secured and stored for thousands of years. What if we reprocess it instead? Politically, it's not an option for now because of nuclear proliferation woes. But in 50, 100, or 200 years when every country on Earth has nuclear weapons, it will make a lot of sense. Why should we operate under the assumption that nuclear waste will have to be safeguarded for 8000 years, rather than 200?

Make up your mind!!!

Hermann Minkowski had proposed in 1908 that light momenta is proportional to a material's refractive index then the following year, another German theorist, Max Abraham proposed the opposite -- momentum is inversely proportional to a material's refractive index.

"Given this result, Minkowski has been declared the new winner and light momenta is directly proportional to the material it is travelling through."

And yet Abraham is declared the winner in TFA and Abraham's equation says it's inversely proportional.

Actually, I know quite a bit about (stochastic*) computational physics and the notion that "repeatable" means "can run the exact same simulation with the exact same seed and get the exact same result" is absolutely incorrect. What is meant by "repeatable" is that one can extract from the simulations some sort of macroscopic quantity (usually a thermodynamic quantity or a correlation function) whose average is consistent across many separate runs (known in the biz as the ensemble average). So, for instance, if I'm observing the coalescence of polymers into a hex-phase (as in [1]), I could measure the average number of aggregated copolymer blocks and compare those (as was done in that paper).

Let's make an extended gambling analogy. Suppose I have a new roulette table that I want to certify that it works like it should. One suggestion (akin to what you said), would be to put the entire table under the same initial conditions as a known-good table and see if it gives the same results. A more sophisticated approach would be to make a histogram of results for a large number of independent roles and see if it converges to the proper distribution (or, in case the distribution isn't known theoretically, compare it to the distribution from a different device, also tested a large number of times). I would argue that the second method is much more powerful than the first, because it probes a more relevant value. Nobody cares whether the roulette table gave 00 the first time and 23 the second time -- we are only concerned that, on average, it gives 00 with the same probability as 23.

In stochastic computational simulations, the same story applies. Nobody cares whether a particular simulation did X or Y or Z because that's not relevant. What is relevant is the (converged) probability that, given some starting condition, the systems ends up in X or Y or Z.

* None of these comments apply in any way to solving deterministic systems. You don't need random numbers for those anyway.

** Another commenter pointed out that exact repeatability is incredibly useful for debugging purposes. That is true but that has nothing to do with reproducibility in the scientific sense of the word.

[1] http://link.aip.org/link/?JCPSA6/128/184906/1

At the risk of adding something substantive to the conversation, Physics Today just covered this topic: Environmental consequences of nuclear war.

They seem to think nuclear winter isn't that far fetched. The link is to an HTML summary at Physics Today, but there's also a link there to the PDF of the paper.

Most areas of science strongly rely on philosophy, and most scientists understand it poorly, usually to the detriment of the technical quality of their work.

What a foolishly over-general remark.

Fine, there are scientists who are armchair philosophers in their spare time. But the vast majority of published scientific work does not intersect with philosophy in any way that meaningfully impacts its technical quality. Hardly anyone publishes papers whose technical content involves, say, free will, or any other serious philosophical issue. If you're want to include "the scientific method", you have to provide evidence that scientists' philosophical misunderstandings of their own methods usually have a detrimental impact on their technical work. A few cherry-picked anecdotes of particularly philosophical work doesn't count.

If you disagree, please go to, say, the last issue of Physical Review Letters and enumerate the papers for which the authors' poor understanding of philosophy had a significantly detrimental impact on the technical quality of the paper.

This is the best description of what the paper is likely about, from mr_roboto over on metafilter:
http://www.metafilter.com/76452/Darwin-extended#2336682

"This paper involved two research efforts: first, the authors developed a history of the evolution of a certain class of proteins. That is, they came up with a model that described which mutations occurred to proteins in this class, mutation by mutation, since proteins that look like these proteins first appeared. They looked at how each of these mutations changed a certain property of the proteins, and found that rather drifting gradually through all possible values of this property, each mutation forced the property to go to an extreme of its possible values: either maximizing it or minimizing it.

In the second part of the work, they applied a mathematical theory called "optimal control theory" to the history developed in the first part. This theory allows for the creation of a bunch of mathematical abstractions corresponding to "systems" with "inputs" and "outputs", and it describes how to most efficiently change a system such that, given a defined input, it produces a desired output. It turns out that the evolutionary history of this class of proteins is consistent with a kind of optimal control; that is, the mutations that appear over the history of this class of proteins--those same mutations that flip back and forth between a set of extremes--behave as if they are determined by an efficient solution to a control problem."

Metafilter also links to the paper itself (behind a paywall):
http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000100000025258103000001&idtype=cvips&prog=normal

DNA repair is not the issue. They haven't modified DNA at all. They have modified the resulting proteins and measured their redox potential. The paper looks at the statistics of how the redox potential changes, and concludes that this is consistent with optimal control.

This seems to me to be a headline grabber with little to no actual relevance to the research within.

Agreed.

The paper; I think it's free.

http://www.aip.org/pnu/2002/split/599-2.html

http://www.sciencebits.com/ice-ages

http://physicsworld.com/cws/article/news/19866

There is an excellent essay in Spencer and Weart on the history of this connection, from William Herschel's suggestion of Sun-induced climate variability in 1801, to the widespread interest in 1850.

In short, nobody has been able to demonstrate that the total energy reaching the earth from the Sun changes by more than about 0.1%. As early as 100 years ago we knew this figure was under 1%.

People try to link global warming to all sorts of things, for all sorts of deluded reasons. If you have the time, or find yourself engaging with people who dispute the consensus position, do put aside an hour or so for reading the The Modern Temperature Trend essay, or the history section of the IPCC AR4 - though I found Spencer & Weart much more engaging. A lot of people arguing against the consensus haven't read the history and often don't know that the arguments they're putting forth as if nobody ever thought of it before were discredited decades ago.

There is an excellent essay in Spencer and Weart on the history of this connection, from William Herschel's suggestion of Sun-induced climate variability in 1801, to the widespread interest in 1850.

In short, nobody has been able to demonstrate that the total energy reaching the earth from the Sun changes by more than about 0.1%. As early as 100 years ago we knew this figure was under 1%.

People try to link global warming to all sorts of things, for all sorts of deluded reasons. If you have the time, or find yourself engaging with people who dispute the consensus position, do put aside an hour or so for reading the The Modern Temperature Trend essay, or the history section of the IPCC AR4 - though I found Spencer & Weart much more engaging. A lot of people arguing against the consensus haven't read the history and often don't know that the arguments they're putting forth as if nobody ever thought of it before were discredited decades ago.

Read this latest, from the American Institute of Physics: http://ptonline.aip.org/journals/doc/PHTOAD-ft/vol_61/iss_9/47_1.shtml Scroll down to the bottom and look at the bullet points: # In 1982 China's premier Deng Xiaoping began the transfer of nuclear weapons technology to Pakistan and, in time, to other third world countries. Those transfers included blueprints for the ultrasimple CHIC-4 design using highly enriched uranium, first tested by China in 1966. # A Pakistani derivative of CHIC-4 apparently was tested in China on 26 May 1990. --- Why was this published only now? The US has known about this information for quite some time, but sat on it, for security reasons. But now the US is finally telling China that enough is enough, and that it can't expect to wantonly proliferate nuclear weapons technology without facing consequences.

Oh really! Are you certain? Scientific justification seem plentiful to me. Maybe your emotions are clouding you judgment?

I don't mean to be offensive, but almost all those numbers are just pulled from your ass (and I am sure you'll agree).

For the record, today exist technologies for depositing atomic monolayers of various oxides and even elements. Also, if you think of it, CNTs are nothing more than graphene cylinders - therefore, a carbon atom monolayer.

Furthermore, CMOS transistors with 17nm long gates have been fabricated already in the distant 2006. Planar CMOS with gates of 15nm have been fabricated in "prehistoric" 2001! And if you think that is impressive, check out this article from the even more distant past

So, 22nm is far from a physical limit, which is a statement easily demonstrated - by historical events, so to say.

Yes, I can. I think this technique is based on research described here:

Darks Physics Beats Light Limit

Paper:

Resonant Interferometric Lithography beyond the Diffraction Limit

The following review can be interesting: Nanomaterials and nanoparticles: Sources and toxicity

Biointerphases -- December 2007 -- Volume 2, Issue 4, pp. MR17-MR71

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=VIRT01000017000017000001000001&idtype=cvips&gifs=Yes&type=ALERT

55 pages though - not for those who don't like to RTFA...

traditionally, science forms its hypothesis, and performs an experimentum crucis to test the hypothesis; rinse & repeat. it seems to me that 'the cloud' refers to a hitherto statistically huge number of samples of data points from which to extract our knowledge of the world -- a sort of broad collection of facts derived from constantly and systematically varying the experimental conditions -- an exploratory experimentation. goethe outlines a method of Exploratory Experimentation in the essay The experiment as mediator between subject and object.

"Theory-oriented and exploratory experimentation are not exclusive categories, but rather members of a spectrum of experimental research strategies. Which is more productive in a given context depends on many factors, including a field's state of development, the sort of knowledge (for example, underlying mechanisms versus phenomenal regularities) sought by the physicist, and the complexity of the system being studied. Our aim in emphasizing the exploratory path has been to bring to light an experimental style that has played an important, but hitherto underrecognized, role in the history of physics.

Physics Today Article

The damage can occur from the exhaust gas pressure from the rocket motors
as well as the the acoustic pressure. Also, there is a system in place that is used
to dampen the sound levels from the launch that would otherwise damage the
flamepit, as we see in those photos, that dumps huge quantities of water
into the flamepit moments before the engines ignite. That quantity of water
could, in and of itself, be partially responsible for the damage that is seen
in the photos. Once those bricks are loosened or dislodged, they would be carried
out of the flamepit by the force of the rocket motor exhaust gases.
There was a study done back in 1989 that measured the SPL of the solid rocket motors
at an amazing 196db 1000 feet from the launch pad. At some point on the db scale for SPLs
the SPL becomes measurable in actual PSI over-pressures. That means the soundwaves themselves
are exerting significant physical pressure on the launchpad and surrounding structures, which
could under the right conditions, be damaged by those forces.

Yes, he did. Rider's argument has also been shown to be invalid: http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000004000004001039000001&idtype=cvips&gifs=yes

"In particular Bussard claimed that the monoenergetic velocity distribution in the plasma was periodically restored without input of energy."

Ion upscattering was addressed pretty conclusively by Chacon here:

http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000007000011004547000001&idtype=cvips&gifs=yes

"In spherical Penning fusion devices, a spherical cloud of electrons, confined in a Penning-like trap, creates the ion-confining electrostatic well. Fusion energy gains for these systems have been calculated in optimistic conditions (i.e., spherically uniform electrostatic well, no collisional ion-electron interactions, single ion species) using a bounce-averaged Fokkerâ"Planck (BAFP) model. Results show that steady-state distributions in which the Maxwellian ion population is dominant correspond to lowest ion recirculation powers (and hence highest fusion energy gains). It is also shown that realistic parabolic-like wells result in better energy gains than square wells, particularly at large well depths (>100 kV). Operating regimes with fusion power to ion input power ratios (Q-value) >100 have been identified."

Here was Bussard's take:

"Ions spend less than 1/1000 of their lifetime in the dense, high energy but low cross-section core region, and the ratio of Coulomb energy exchange cross-section to fusion crosssection is much less than this, thus thermalization (Maxwellianization) can not occur during a single pass of ions through the core. While some up- and down- scattering does occur in such a single pass, this is so small that edge region collisionality (where the ions are dense and âoecoldâoe) anneals this out at each pass through the system, thus avoiding buildup of energy spreading in the ion population (Ref. 14). Both populations operate in non-LTE modes throughout their lifetime in the system. This is an inherent feature of these centrally-convergent, ion-focussing, driven, dynamic systems, and one not found (or even possible) in conventional magnetic confinement fusion devices."

You don't necessarily need to add energy to reorder a system, if reordering puts things back to their lowest energies. Consider some balls lined up at the bottom of a V-shaped well. You disorder them, they bounce around in the V but reorder at the bottom of the well again because that's their lowest energy point. It required energy to disorder them, but no additional energy was added to reorder them.

For anyone curious about the actual experiment whose data was recovered:

The abstract for the science experiment is at http://link.aps.org/abstract/PRE/v77/e041116 (or in the table of contents issue is http://scitation.aip.org/dbt/dbt.jsp?KEY=PLEEE8&Volume=77&Issue=4 ).

"We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids, near the critical point of xenon. The data span a wide range of reduced shear rate ... The measurements had a temperature resolution of 0.01 mK and were conducted in microgravity aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity."

Some better examples:

• The Great Brass Brain, an analog tide predictor. It was built in 1910, and used until 1966, for regular tide predictions.
• The Bay Model, a working 1.5 acre model of water flow in San Francisco Bay. Built in 1956, in use until 2000. (You can still visit, but it's not used as a research tool any more.)
• SCEPTRON, a mechanical filter bank of quartz fibres which could record and play spectra onto photographic film. This was trainable as a speech recognition system. Early 1960s.
• The Iconarama., the USAF's Etch-A-Sketch. This was one of the first large screen displays, basically a plotter/slide projector combo. It could write, but not erase selectively, so units were used in pairs, allowing a redraw by the unit not projecting, then a lamp switch. 1950s.

Agreed. True WMD (as opposed to dirty bomb) detection is even worse. Turns out you're not looking for the U-235 but instead the easier-to-see U-238 that was not removed during the enrichment process. It's still trivially easy to shield your small fissile core during transport with a couple of hundred pounds of lead. See this and this and this for interesting details.

Actually, the earliest concern over greenhouse gases that I'm aware of was proposed in 1896, by Svante Arrhenius. The American Institute of Physics has a pretty extensive bibliography as part of their review paper on this subject, which goes back even further than this.

See The Discovery of Global Warming