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Radioactive Tool Goes Missing In Texas

volsung Re:Americium? (163 comments)

Yeah, you don't want to mess with neutron sources. Fast neutrons penetrate lots of materials (due to the lack of charge), much like gammas, and can produce short-lived isotopes that continue to decay after the source has been removed.

about 2 years ago
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Radioactive Decay Apparently Influenced By the Sun

volsung Re:Neutrinos? (267 comments)

Since you mention neutrinos, it is also worth noting that there was similar discussion (5 or so years ago) as to whether we can observe periodic variation in the number of neutrinos seen on Earth using various experiments. (Note that periodicities in neutrino rates are not what physicists call "neutrino oscillations". That's an entirely different effect.) Those papers claiming a periodicity included one of the authors on this study of radioactivity decay, and the analysis techniques were disputed by other papers as giving an unacceptably high rate of false positives. The experiments presented counter-analyses showing no significant signal once the probability of false positives was dealt with. (Disclaimer: I was tangentially involved in one of those papers.)

I haven't looked closely enough at the radioactive decay papers to see if the same issue has cropped up again here, but the neutrino periodicity argument is a good example of how these signals can fall apart under closer scrutiny.

about 2 years ago
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Radioactive Decay Apparently Influenced By the Sun

volsung Re:This is exciting (267 comments)

Another relatively easy control would be to conduct simultaneous experiments in the northern and southern hemispheres. Many external effects (like temperature) would be 180 degrees out of phase, while the distance from the Sun will be essentially the same for the two experiments.

about 2 years ago
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Radioactive Decay Apparently Influenced By the Sun

volsung Re:This is exciting (267 comments)

I think the problem is that the link is not yet established. What we have is a link between count rates in a detector observing a sample of some isotope and time of year, which no one disputes (we reasonably assume they are not making up their data). The argument is whether you can make the inductive leap to the claim that radioactive decay rates depend on the amount of solar radiation. As shown in some of those papers above, other experiments don't (like the test with the MESSENGER probe) show the effect you would expect if solar radiation were the cause.

Even if we do find there is an external influence on decay rates (which would be pretty nifty), that definitely does not imply that the times of individual radioactive decays are predictable.

about 2 years ago
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Radioactive Decay Apparently Influenced By the Sun

volsung Re:This is exciting (267 comments)

This argument about solar influence on nuclear decay rates has been going on for a few years now. The experimental issues are hard to interpret, because you have to be able to rule out external influences on your counting apparatus. It is extremely hard when the period of your signal matches the orbit of the Earth, which aliases all sorts periodic behavior that has nothing to do with new physics. There are seasonal variations in temperature, cosmic rays, the voltage delivered by the power company, foot traffic near your lab, etc, etc. Verifying that none of these things can possibly influence your results is what takes all the time.

A semi-random selection of earlier papers on the subject:

"Experimental investigation of changes in beta-decay count rate of radioactive elements" (1999):
Claiming 24 hour and 27 day periodicities in the decay rates of cobalt-60 and cesium-137
http://arxiv.org/pdf/hep-ex/9907008v1.pdf

"Power Spectrum Analyses of Nuclear Decay Rates" (2010):
Reports of an annual periodicity in the decay rates of chlorine-36, silicon-32, manganese-56, and radium-226.
http://arxiv.org/abs/1007.0924

"Solar Influence on Nuclear Decay Rates: Constraints from the MESSENGER Mission" (2011)
A study of cesium-137 decay rates on a spacecraft going to Mercury show no change as the spacecraft travelled closer to the Sun.
http://arxiv.org/abs/1107.4074

"Search for the time dependence of the 137Cs decay constant" (2012)
Cesium-137 decays in a detector underground (shielding it from most cosmic rays) show no significant periodicity, with limits much lower than claimed signals.
http://arxiv.org/abs/1202.3662

"Power Spectrum Analysis of LMSU (Lomonosov Moscow State University) Nuclear Decay-Rate Data: Further Indication of r-Mode Oscillations in an Inner Solar Tachocline" (2012)
Studies of strontium-90 decays show a variety of periodic variations, ranging from 0.26 per year to 3.96 per year.
http://arxiv.org/abs/1203.3107

This list goes on and on. There is hardly any consensus on the issue.

about 2 years ago
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Windows Has a Future In RAM: AgigaTech Samples DDR3+Flash DIMM

volsung Re:I don't see it (139 comments)

One of the advantages laptops have over desktop computers is effectively a built-in, relatively lightweight UPS. When someone kicks out the cord on my laptop, I don't even notice, but on my desktop, that would be very annoying. If some upgraded RAM/Flash + operating system support would allow hibernation on a desktop when the power was cut, that would be very handy. Some thought would have to be given to how this should interact with filesystems, since the hard drive would instantly lose power as well. Any writes in progress would have to be reattempted when the system booted up again.

Of course, the main problem is that laptops are quickly becoming people's desktops, and that might kill the market for this before it even starts.

about 2 years ago
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Advance Warning System For Solar Flares Hinges On Surprising Hypothesis

volsung Re:Variable rate of decay? (199 comments)

Just FYI: Nearly all physics articles from the last 15 years are posted in "preprint" form on the arXiv before submission to a journal. The arXiv is completely free, and is where nearly all physicists read papers from, rather than from the journals themselves.

Just Google the title of the paper you are interested in, and you usually find the preprint version:

http://arxiv.org/abs/1205.0205

about 2 years ago
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Baker Has to Make 102,000 Cupcakes For Grouponers

volsung Re:Groupon needs a staggered approach (611 comments)

There already is a simple limit scheme available, but this business owner chose not to use it. Presumably this failure was a combination of lack of due diligence by the business owner and some pressure from Groupon sales staff. Groupon assumes that few businesses will ever offer a deal through them twice, so their strategy seems to be squeezing as many sales out of them as possible, margins and customer quality be damned.

Hopefully stories like this will make more small business owners aware of the risks associated with massive cut-rate promotions through sites like Groupon.

more than 2 years ago
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Flooding Takes Major Hard Drive Plant Offline; Shortages Predicted

volsung Re:Who cares? We have the cloud to save us! (203 comments)

I have often wondered what the total amount of temporary packet storage in the world's routers is.... How much data can actually be in transit at any given time?

more than 2 years ago
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Tesla Model S: 0-60 In 4.5 Seconds

volsung Re:Wait for Top Gear (426 comments)

Moreover, why do we need to adopt Highlander Rules here? An electric car is a practical replacement for people whose driving habits don't require a fuel station on every corner. That doesn't work for everyone, and those people shouldn't buy a pure electric car.

However, complaints about the range issue do highlight one of the real problems in selling electric vehicles: discomfort in giving up some capability regardless of how often you actually use that capability. I owned my first car (quite the beater) for two years, and drove it more than 150 miles from home exactly once. Would I have been happy with a vehicle that had a 300 mile range? Sure. (Would I have spent $200k rather than $2k? No, but I would not have spent that much money on a car, even if I never had to refuel it.)

more than 2 years ago
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Tesla Model S: 0-60 In 4.5 Seconds

volsung Re:320 miles (426 comments)

Because that's what he said?

"The 300-mile range Tesla would suffice for about 90% of my driving. 90%, but not 100%, so I still have to own another vehicle for the remainder."

I'm not sure how else to interpret that statement without stuffing words into the author's mouth.

more than 2 years ago
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Tesla Model S: 0-60 In 4.5 Seconds

volsung Re:320 miles (426 comments)

I think you mean "Apple management."

more than 2 years ago
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Why We Don't Need Gigabit Networks (Yet)

volsung Re:Editing. (359 comments)

For the software end of this, check out CrashPlan. It saves incremental backups of your system to external hard drives, your friend's computer (also running CrashPlan) and/or the CrashPlan servers. It's great stuff, and works on Win/Mac/Linux. Plus, your backup data is encrypted before it leaves your computer, so you don't have to worry about the security of your friend's computer. (By default, your data can be decrypted on the CrashPlan server in order to support web access to your files. If you don't want that, you can set an encryption password that CrashPlan can't access, and then no one can see your data outside of your computer.)

more than 2 years ago
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Ask Slashdot: Overcoming Convention Hall Wi-Fi Interference?

volsung Re:Partial solution: go 5 GHz (251 comments)

BTW, keep in mind that 802.11n is not synonymous with 5 GHz support. Some devices list 802.11n, but still only work on 2.4 GHz.

about 3 years ago
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Ask Slashdot: Overcoming Convention Hall Wi-Fi Interference?

volsung Partial solution: go 5 GHz (251 comments)

For the devices that support it (decent laptops, iPad, and possibly other tablets), going to the 5 GHz band is a huge win. There are plenty of non-overlapping channels, and congestion is lower. The problem is that most WiFi enabled phones only support the 2.4 GHz band, so this will not cover all cases.

about 3 years ago
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Swede Arrested For Building Nuclear Reactor

volsung Re:How was this going to work? (410 comments)

Yes, I am aware of what is for sale, since we buy these things for our lab. (Although our sources are low enough in intensity to avoid the tracking required for the big boys.) I am confused by the use of the term "reactor" which is typically used to describe a device that is designed to produce fission reactions (or fusion, if you are a Farnsworth kind of person).

Generating fission is different than having a bunch of things that undergo radioactive decay. You need some neutrons, and a fissile material. It sounds like the (alpha, n) reaction on beryllium is a reasonable guess for neutron production, and you can use the neutrons to induce fission on uranium, even if it won't be remotely self-sustaining.

about 3 years ago
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Swede Arrested For Building Nuclear Reactor

volsung How was this going to work? (410 comments)

I'm puzzled how this guy was going to build a "nuclear reactor" out of mail-order isotopes and smoke detectors. Smoke detectors usually contain Am-241, which is an alpha emitter. The mail order stuff I assume was uranium ore. Was he planning to create neutrons from (alpha, n) reactions and use those to trigger a few fissions from the uranium?

This sounds like his experiment bears as much similarity to a reactor as a balloon full of hairspray resembles a car engine.

about 3 years ago
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Why People Should Stop Being Duped By the 3D Scam

volsung Re:Oh for goodness sake (394 comments)

Internet Selection Effect. (AKA "self selection bias + online discussions") The comment distribution is generally shifted toward angry rants about the topic. It turns out that anger plus a sense of "rightness" provides good emotional fuel to convince someone to click the "Reply" button.

more than 2 years ago

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