Search found 941 matches

by Minerva
Tue Sep 26, 2017 11:01 am UTC
Forum: Science
Topic: Metal permittivity
Replies: 0
Views: 894

Metal permittivity

Given a known bulk plasma frequency (say 3.7 PHz for aluminium), and a known incident wavelength (say 500nm), what's the expression for the relative permittivity of the metal? For context, consider a plasmonic device that acts as a filter, with a nanoscale grid of holes in metal. The maximum transmi...
by Minerva
Wed Mar 01, 2017 5:00 am UTC
Forum: Science
Topic: Magnetic field from a permanent magnet
Replies: 1
Views: 1580

Magnetic field from a permanent magnet

Consider a small cylindrical neodymium permanent magnet, suppose it is say 5mm diameter and 5mm high for the sake of example. The magnet engineering data from real-world vendors typically provides the remanence, coercivity, max energy product, etc. http://www.arnoldmagnetics.com/en-us/Products/Neody...
by Minerva
Wed Mar 01, 2017 4:51 am UTC
Forum: Science
Topic: Storing Nuclear Waste on the Moon
Replies: 57
Views: 8208

Re: Storing Nuclear Waste on the Moon

If nuclear waste is so terrible, then don't waste it! Wasting used-once LWR fuel, with 97% unreacted good fuel, is a terrible idea. We can make containers that will survive launch vehicle accidents. RTGs are designed to do just this. For example the Apollo 13 ALSEP fuel cask survived uncontrolled at...
by Minerva
Sat Nov 12, 2016 4:42 am UTC
Forum: Science
Topic: V=IR - bad science or am I being thick?
Replies: 15
Views: 3469

Re: V=IR - bad science or am I being thick?

V=IR is very "good" science, at least if every bit of electrical engineering people have ever built is anything to go by. "The higher the resistance the harder the battery has to work to maintain a usable voltage and so the amount of power it can produce per charge decreases." Th...
by Minerva
Fri Sep 23, 2016 4:52 pm UTC
Forum: Science
Topic: Excluding the phylogenetic relationship from a phylogenetic vector
Replies: 3
Views: 1667

Re: Excluding the phylogenetic relationship from a phylogenetic vector

Thanks :)

Code: Select all

def crossprod(x,y):
      return sum(map(operator.add, x,y))


That's supposed to be an

Code: Select all

operator.mul
or something like that, right?
by Minerva
Tue Sep 13, 2016 2:15 am UTC
Forum: Science
Topic: Excluding the phylogenetic relationship from a phylogenetic vector
Replies: 3
Views: 1667

Excluding the phylogenetic relationship from a phylogenetic vector

Paper here. http://bioinformatics.oxfordjournals.org/content/21/17/3482.full.pdf In particular, note the projection operator, section 2.3, and equation (2) and equation (3). Given a couple of vectors, u and v (well, nu actually, but can't be bothered typesetting it, and LaTeX makes the page too slow...
by Minerva
Tue Sep 13, 2016 2:02 am UTC
Forum: Science
Topic: Reversing entropy with unlimited energy
Replies: 9
Views: 2882

Re: Reversing entropy with unlimited energy

In a localised system, yes, we do it all the time. That's how your air conditioner or refrigerator works. Or the clean patch on my desk that allows me to reach past junk to reach the keyboard, or essentially anything else in the universe that works with expended effort to generate a local reduced-en...
by Minerva
Tue Sep 13, 2016 1:43 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1732: "Earth Temperature Timeline"
Replies: 523
Views: 61676

Re: 1732: "Earth Temperature Timeline"

Am I missing something? the graph in the comic doesn't change scale. But maybe it should change scale. Is this completely linear time scale really that useful? Obviously it's a fun excuse for an enormous comic, but for the best possible understanding of the changes industrialisation has made, perha...
by Minerva
Tue Jun 07, 2016 11:57 pm UTC
Forum: Science
Topic: Tonic Water
Replies: 17
Views: 4988

Re: Tonic Water

As well as the direct effect of temperature on taste, or beverage "experience" overall, the temperature is also likely to affect the rate of CO2 loss from a carbonated beverage, and the "going flat" of the beverage is presumably one of the biggest factors that diminishes the taste.
by Minerva
Tue Jun 07, 2016 11:53 pm UTC
Forum: Science
Topic: Alkaline Food
Replies: 26
Views: 5270

Re: Alkaline Food

For getting a more alkaline diet, this book lists foods such as banana, celery, lettuce, mung bean sprouts, and spring onion. There is a huge amount of snake oil and quackery out there surrounding "alkaline diets". Many of them will even tell you that lemons and limes are alkaline! (Big L...
by Minerva
Sat Nov 07, 2015 1:36 am UTC
Forum: Science
Topic: Sun as final storage for radwaste?
Replies: 134
Views: 23907

Re: The sun as a nuclear waste incinerator

CutmanCometh wrote:Why can't we round up all the spent fuel rods from nuclear power plants, load them on a rocket, and fly them into the sun?


Because that's a huge resource of valuable nuclear fuel, it's good stuff and we shouldn't waste it!
by Minerva
Sat Nov 07, 2015 1:34 am UTC
Forum: Science
Topic: Diamagnetism and MRI
Replies: 5
Views: 2073

Re: Diamagnetism and MRI

I guess you could say that paramagnetism is important in the context of gadolinium MRI contrast compounds - but that's paramagnetism, not diamagnetism.
by Minerva
Sun Oct 04, 2015 6:25 am UTC
Forum: Science
Topic: Nuclear explosion powerplant
Replies: 31
Views: 5232

Re: Nuclear explosion powerplant

It has been proposed and seriously studied. Somebody mentioned PACER above. If you set up a Teller-Ulam design so that the secondary (fusion) stage provides most of the energy, the fusion fraction (as a fraction of the overall energy yield) is as high as possible, the primary is very small (and the ...
by Minerva
Wed Sep 09, 2015 6:29 pm UTC
Forum: Science
Topic: How do (wifi) antennas get their shape?
Replies: 4
Views: 2135

Re: How do (wifi) antennas get their shape?

How are they designed that way? It's a little bit of a craft, and sometimes a little bit of black magic, and sometimes a little bit of finite-element computational simulation of Maxwell's equations. An antenna, basically, is an impedance-matching transformer that goes between the 50-ohm transmission...
by Minerva
Fri Jun 12, 2015 6:06 pm UTC
Forum: Books
Topic: What are you readioactive now(and other book related stuff)?
Replies: 1806
Views: 407647

Re: What are you readioactive now(and other book related stu

I'm reading Neal Stephenson's new novel - Seveneves . I've read apocalyptic fiction before, but never have I actually felt some sort of sense of what it would be like for the world to end. I'm getting that from this book. Probably because it's so current, and so detailed, and so well written. It's ...
by Minerva
Fri Jun 12, 2015 6:00 pm UTC
Forum: News & Articles
Topic: Chocolate causes weight loss academic paper was a hoax
Replies: 32
Views: 10826

Re: Chocolate causes weight loss academic paper was a hoax

It's just like the famous Sokal "experiment".

If it highlights very clearly, for everybody to understand, where the problems are and where we can improve things, and how - for journalists, for science communicators, for scientists - isn't that a good thing?
by Minerva
Fri Jun 12, 2015 5:58 pm UTC
Forum: Movies and TV Shows
Topic: Jurassic World
Replies: 56
Views: 6138

Re: Jurassic World

While watching the film, there was a moment where I thought of this:

http://xkcd.com/135/
by Minerva
Wed May 20, 2015 10:31 am UTC
Forum: Science
Topic: Contamination of insulin pump cartridges
Replies: 23
Views: 3781

Re: Contamination of insulin pump cartridges

You may find this interesting with regards to what the Zn does.

http://www.europeanreview.org/wp/wp-con ... ds/176.pdf
by Minerva
Sat Feb 28, 2015 2:29 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1490: "Atoms"
Replies: 92
Views: 15865

Re: 1490: "Atoms"

The rated life for the electronics in a pacemaker in the early 1970s was only 5 years. I'm impressed with that NEJM letter... if the pacing configuration is still working well for the patient, and our Voyager-lady is still ticking along happily 40 years later, then everyone wins. No further surgery...
by Minerva
Sat Feb 28, 2015 2:05 pm UTC
Forum: Science
Topic: Oxidisers
Replies: 30
Views: 5289

Re: Oxidisers

Of course the list isn't finite. It's infinite, but countably so. If we're talking just chemistry, and are ignoring practicalities such as cosmology and stuff, is there any reason, chemically, why there can't be an infinitely long alkane chain with various functional groups along it? That way, you ...
by Minerva
Thu Jan 22, 2015 4:44 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1474: "Screws"
Replies: 96
Views: 29827

Re: 1474: "Screws"

Godiva is a critical assembly, basically two hemispheres of HEU that can be moved together to reach criticality, for measurements of critical mass, neutron multiplication and things like that. A rather crude, and naked, nuclear reactor. It's basically the same sort of experiment that Harry Daghlian ...
by Minerva
Wed Jan 21, 2015 5:03 pm UTC
Forum: Science
Topic: Interplanetary probe
Replies: 3
Views: 2964

Re: Interplanetary probe

Interplanetary probe? You mean like the Voyagers, the Pioneers, Viking, the Venera program, Mars Science Laboratory, New Horizons, Galileo, Cassini/Huygens, MESSENGER, the Mars Exploration Rovers, and all the rest of them? Yes. It seems like a pretty obvious yes. Did you mean to say something like i...
by Minerva
Wed Jan 21, 2015 4:44 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1474: "Screws"
Replies: 96
Views: 29827

Re: 1474: "Screws"

From our friends at Los Alamos, here's a nice drawing of the Godiva assembly and her uranium screws. The full description can be found in LA-1614, written in 1953. http://library.lanl.gov/cgi-bin/getfile?00318386.pdf There are other devices that contain uranium screws, but I'm not aware of any detai...
by Minerva
Fri Jan 09, 2015 6:23 pm UTC
Forum: Science
Topic: Oscilloscope Stray Signals
Replies: 36
Views: 8051

Re: Oscilloscope Stray Signals

Yes, if you touch the end of an oscilloscope probe it's pretty typical to see a messy sine wave at 50 (or 60) Hz from mains grid hum.

The audible hum if you touch the end of a plug connected to an audio amplifier input is exactly the same thing.
by Minerva
Fri Jan 09, 2015 6:08 pm UTC
Forum: What If?
Topic: What-If 0124: "Lunar Swimming"
Replies: 60
Views: 25412

Re: What-If 0124: "Lunar Swimming"

Sulfur hexafluoride is actually pretty inert chemically. It should be fine with about 20% oxygen added to it as a breathing atmosphere. The slow speed of sound changes the pitch of your voice, though - the opposite of helium which is very light and has a fast speed of sound. But screw building a dom...
by Minerva
Mon Dec 01, 2014 4:52 pm UTC
Forum: News & Articles
Topic: Rossi Cold Fusion Validated by Swedish Skeptic's Society
Replies: 77
Views: 18628

Re: Rossi Cold Fusion Validated by Swedish Skeptic's Society

Actually, we can forget about the Bethe-Weizsäcker formula, gamma-ray spectroscopy, Coulomb potentials, the curve of binding energy or anything like that. Just send in James Randi to inspect the system, consult with any experts he chooses, look at what's going on and set up an experiment and documen...
by Minerva
Mon Dec 01, 2014 4:49 pm UTC
Forum: Science
Topic: Copper Chemical Plating
Replies: 1
Views: 1107

Re: Copper Chemical Plating

You can easily see the same kind of effect quite easily if you get a piece of say, iron, and put into a solution of copper sulfate or something like that. It will certainly happen without electricity, for some combinations of metals. Electroplating will typically produce a thicker, more controlled, ...
by Minerva
Thu Sep 11, 2014 2:14 pm UTC
Forum: Science
Topic: [Physics] Curie and Becquerel
Replies: 13
Views: 4137

Re: [Physics] Curie and Becquerel

list/table with isotopes of the most common elements and their radioactivity density (how many Ci or Bq per g). The quantity you're looking for is what's called the specific activity , and a convenient way to look it up is to look up the Wolfram Alpha page for whichever radionuclide you like. Furth...
by Minerva
Sun Aug 03, 2014 2:14 pm UTC
Forum: Science
Topic: EMDrive and other reactionless propulsion claims
Replies: 71
Views: 13623

Re: EMDrive and other reactionless propulsion claims

When they document the method and experiment in detail allowing it to reproduced and it is accepted by a credible, peer-reviewed scientific journal and published, then at that time we've got N = 1 positive results claimed. And then other scientists can try and reproduce that single claimed positive ...
by Minerva
Wed Jul 02, 2014 3:27 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1389: "Surface Area"
Replies: 125
Views: 31713

Re: 1389: "Surface Area"

I think it would be really cool to show the portion of Titan's surface area which is covered by its rivers and oceans.
by Minerva
Sun Jun 01, 2014 5:34 am UTC
Forum: News & Articles
Topic: Does traditional debate reinforce White Privilege?
Replies: 96
Views: 18265

Re: Does traditional debate reinforce White Privilege?

I used to do debate, many years ago, in school. A little bit at university too. We were pretty good at it. But one day I had an epiphany. This (debate) is bullshit, and I'm going to stop doing it. You decide what's true on the toss of a coin, and you break out your whole arsenal of logical fallacies...
by Minerva
Sun Jun 01, 2014 5:23 am UTC
Forum: Serious Business
Topic: Ethical basis for environmentalism
Replies: 69
Views: 15270

Re: Ethical basis for environmentalism

I agree with environmentalism as a basic underlying ethical idea, but where environmentalism gets into trouble is where it strays into anti-technology or science-denial with regards to the actual implementation of environmentally friendly technology, for example nuclear power science-denial. Also, e...
by Minerva
Tue May 27, 2014 2:29 am UTC
Forum: Science
Topic: Solar Road Ways
Replies: 82
Views: 11665

Re: Solar Road Ways

Also, if you've got a road covered with snow and ice, the snow and ice doesn't absorb enough solar radiation to melt it , let alone allow the solar radiation to be transmitted through the snow and ice to reach a solar cell which converts the light to electricity with substantial inefficiency which p...
by Minerva
Mon May 26, 2014 3:19 pm UTC
Forum: News & Articles
Topic: Isla Vista shooting
Replies: 416
Views: 39120

Re: Isla Vista shooting

and he was autistic in a colloquial sense at least. I swear, every time I have to read somebody on the Internet, or in the press, bring up autism spectrum disorders or Asperger's syndrome etc. in relation to Elliot Rodger and these events I'm going to... well, not go out and kill people. But I'll s...
by Minerva
Mon May 26, 2014 2:55 pm UTC
Forum: Science
Topic: Solar Road Ways
Replies: 82
Views: 11665

Re: Solar Road Ways

Well, it's an IndieGoGo project, alongside many other brilliant examples of careful engineering on IndieGoGo such as "Mayan Quantum Energy Pyramid" and "Home Quantum Energy Generator". (Yes, that's seriously perpetual motion free energy machine on IndieGoGo, complete with obligat...
by Minerva
Mon May 26, 2014 2:20 pm UTC
Forum: Science
Topic: Could we ever replace fossil fuels in aviation?
Replies: 24
Views: 4415

Re: Could we ever replace fossil fuels in aviation?

Replacing fossil fuels in aviation seems to be a relatively difficult "high-hanging fruit" problem that accounts for a small portion of greenhouse gas emissions, compared with other areas like power plants on the ground that account for a large portion of greenhouse gas emissions and fossi...
by Minerva
Thu Mar 20, 2014 6:41 am UTC
Forum: Science
Topic: More atoms in a grain of sand than stars in the universe.
Replies: 5
Views: 16851

More atoms in a grain of sand than stars in the universe.

This is a bit of a quick SWOTI question. I'm fairly confident of the answer, but I just thought I'd throw it open here for peer review, feedback or discussion. Claim: There are more atoms in a single grain of sand than all the stars in the universe. Discussion: The number of galaxies in the observab...
by Minerva
Mon Mar 10, 2014 6:37 am UTC
Forum: Movies and TV Shows
Topic: Cosmos: A Spacetime Odyssey
Replies: 3
Views: 4313

Cosmos: A Spacetime Odyssey

So, this has started up. What do we think? It seems to remain closely faithful to the original Cosmos, but obviously there are some new facts that will be updated, eg. we know for a fact that Sagan's speculative ideas were spot on, and there are rivers and lakes of simple hydrocarbons on Titan. Ther...
by Minerva
Thu Mar 06, 2014 6:01 pm UTC
Forum: News & Articles
Topic: GCHQ spied on 1.8m webcams to test facial recognition
Replies: 5
Views: 2650

Re: GCHQ spied on 1.8m webcams to test facial recognition

"Unfortunately it would appear that a surprising number of people use webcam conversations to show intimate parts of their body to the other person. Aww, innocent little GCHQ discovers what people actually use the Internet for! "there is no perfect ability to censor material which may be ...
by Minerva
Mon Feb 17, 2014 12:13 pm UTC
Forum: News & Articles
Topic: Three men to stand trial for stealing food from a bin
Replies: 23
Views: 4285

Re: Three men to stand trial for stealing food from a bin

http://www.theguardian.com/uk-news/2014/jan/28/three-charged-vagrancy-act-food-skip-iceland It is expected Paul May, a freelance web designer, will argue that he was taking the food because he needed it to eat and does not consider he has done anything illegal or dishonest in removing food destined ...

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