Ostracods, when eaten, release firefly-like bioluminescent chemicals, which cause the fish that's eaten them to glow, which makes them a target for larger predators. So the fish throw up, and the ostracod goes on its merry way.
Sunday, September 7, 2014
Friday, August 22, 2014
Non-newtonian Fluids
"It is within the realm of possibility that you could make a non-Newtonian fluid that is primarily plasma or gas? I've only ever heard of non-Newtonian fluids that are liquid-based." Nick L.
Interesting question. A non-newtonian fluid goes through a reversible phase transition on the application of pressure. That's the definition I'm guessing you are asking about. Really, a non-newtonian fluid is any fluid that doesn't follow Ohm's law of pressure/ resistance to flow = flow rate. Gasses under moderately high vacuum are non-newtonian, because they are in transition from laminar (newtonian) flow into ballistic flow. Plasmas are funky, because they are made of ions, which interact at larger distances. I hadn't really thought about it before, but I suspect that plasma physics does not meet a strict newtonian definition for fluid dynamics.
The classic non-newtonian fluid is a mixture of cornstarch and water. Some people call it ooblek, a name I despise. If you are looking for a gas that goes solid when you step on it, I think you are out of luck. It's much easier to go from a liquid (molecules held together with low energy bonds = "hydrogen" bonds = Van der Waals forces, where the molecules are in causal contact but free to rearrange their positions, to a solid, where the bonds are strong enough to stop the free movement. You can make this happen by cooling the fluid down past the phase transition, or by introducing a magnetic field into a ferrofluid, or by adding pressure to a mixture that allows the liquid portion to move out from between the solids so they jam together.
The trick to running on the cornstarch-water mix is that the cornstarch molecules are complicated, so you can force the water molecules into their structure and out of the solution, reversibly. For something like quicksand, the bed of sand is fluidized by rising water, which you can fall into if you struggle, but float on if you lay flat like floating in plain water.
Interesting question. A non-newtonian fluid goes through a reversible phase transition on the application of pressure. That's the definition I'm guessing you are asking about. Really, a non-newtonian fluid is any fluid that doesn't follow Ohm's law of pressure/ resistance to flow = flow rate. Gasses under moderately high vacuum are non-newtonian, because they are in transition from laminar (newtonian) flow into ballistic flow. Plasmas are funky, because they are made of ions, which interact at larger distances. I hadn't really thought about it before, but I suspect that plasma physics does not meet a strict newtonian definition for fluid dynamics.
The classic non-newtonian fluid is a mixture of cornstarch and water. Some people call it ooblek, a name I despise. If you are looking for a gas that goes solid when you step on it, I think you are out of luck. It's much easier to go from a liquid (molecules held together with low energy bonds = "hydrogen" bonds = Van der Waals forces, where the molecules are in causal contact but free to rearrange their positions, to a solid, where the bonds are strong enough to stop the free movement. You can make this happen by cooling the fluid down past the phase transition, or by introducing a magnetic field into a ferrofluid, or by adding pressure to a mixture that allows the liquid portion to move out from between the solids so they jam together.
The trick to running on the cornstarch-water mix is that the cornstarch molecules are complicated, so you can force the water molecules into their structure and out of the solution, reversibly. For something like quicksand, the bed of sand is fluidized by rising water, which you can fall into if you struggle, but float on if you lay flat like floating in plain water.
Saturday, August 16, 2014
If we went back to the stone age right now and stopped emitting any CO2, in about 100 years would see about 2ºC temperature rise
Wednesday, August 13, 2014
Tuesday, August 12, 2014
Cutaway Bore Obstructions of a Webley Mark IV .38/200 Revolver
I understand the first one. But all eight of them? Maybe it was some sort of performance test.
As seen on Reddit.
Copper foam turns CO2 into useful chemicals
We're going to need to start sequestering CO2 and CH4 if we want to get the runaway greenhouse effect under control.
"The experiments showed that the copper foam converted CO2 into formic acid — a compound often used as a feedstock for microbes that produce biofuels — at a much greater efficiency than planar copper. The reaction also produced small amounts of propylene, a useful hydrocarbon that’s never been reported before in reactions involving copper."
Article from Brown University
"The experiments showed that the copper foam converted CO2 into formic acid — a compound often used as a feedstock for microbes that produce biofuels — at a much greater efficiency than planar copper. The reaction also produced small amounts of propylene, a useful hydrocarbon that’s never been reported before in reactions involving copper."
Article from Brown University
3 in Congress going after SpaceX for cutting into profits of big defense contractors.
"[T]his whole thing looks to me to be a transparent attempt from members of our Congress to hinder a privately owned company that threatens their own interests." - Phil Plait
Article on Slate
Article on Slate
National Suicide Prevention Lifeline
These are good people. 1-800-273-8255
National Suicide Prevention Lifeline
National Suicide Prevention Lifeline
Monday, August 11, 2014
But wait, there's more! Triclosan linked to cancer cell growth!
Like I said before, DON'T USE ANTIBACTERIALS!
Bloomberg News Story on Triclosan
FDA Panel: No Advantage to Antibacterial Soap
EPA List of things that kill norovirus:
Triclosan is not on that list. It's antibacterial, not antiviral.
I am not a doctor. Don't rely on me for medical advice.
Bloomberg News Story on Triclosan
FDA Panel: No Advantage to Antibacterial Soap
EPA List of things that kill norovirus:
Triclosan is not on that list. It's antibacterial, not antiviral.
I am not a doctor. Don't rely on me for medical advice.
Robin Williams
This is awful. Suicide was the 10th most frequent cause of death in the US in 2011.
My friend Elena Day says, "When he (Robin Williams) visited La Nouba (the Cirque du Soleil show Elena performed in), I LITERALLY threw myself at his feet, grabbed his ankle and said, "I love you, Robin!!" He was remarkable. He could say specifically what each person had done in the show and complimented them on it. I'm in shock."
That's as good a eulogy as I can think of.
Robin Williams Death
CDC Stats
My friend Elena Day says, "When he (Robin Williams) visited La Nouba (the Cirque du Soleil show Elena performed in), I LITERALLY threw myself at his feet, grabbed his ankle and said, "I love you, Robin!!" He was remarkable. He could say specifically what each person had done in the show and complimented them on it. I'm in shock."
That's as good a eulogy as I can think of.
Robin Williams Death
CDC Stats
Civilians take control of an abandoned NASA satellite.
This is totally awesome! Civilian space geeks take over control of a decommissioned NASA satellite and open source the data. NASA gave permission for this to happen in an entirely novel agreement.
Link at BetaBeat
Link at BetaBeat
Wire grid polarizers for NASA
Here's a blog post at Tormach of my work, including some video of the dance I programmed into the machine to wind the wire onto the small square grid. More on this in Publications coming up.
http://www.tormach.com/blog/nasa-piper/
http://www.tormach.com/blog/nasa-piper/
Publications: Microwave Optics: Blackbody Calibrator: 2004
Design and Calibration of a Cryogenic Blackbody Calibrator at Centimeter Wavelengths
A. Kogut, E. Wollack, D. J. Fixsen, M. Limon, P. Mirel, S. Levin, M. Seiffert, P. M. Lubin
Review of Scientific Instruments 75 (2004) 5079-5083
We describe the design and calibration of an external cryogenic blackbody calibrator used for the first two flights of the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The calibrator consists of a microwave absorber weakly coupled to a superfluid liquid helium bath. Half-wave corrugations viewed 30 deg off axis reduce the return loss below -35 dB. Ruthenium oxide resistive thermometers embedded within the absorber monitor the temperature across the face of the calibrator. The thermal calibration transfers the calibration of a reference thermometer to the flight thermometers using the flight thermometer readout system. Data taken near the superfluid transition in 8 independent calibrations 4 years apart agree within 0.3 mK, providing an independent verification of the thermometer calibration at temperatures near that of the cosmic microwave background.
http://arxiv.org/pdf/astro-ph/0402580v1.pdf
A. Kogut, E. Wollack, D. J. Fixsen, M. Limon, P. Mirel, S. Levin, M. Seiffert, P. M. Lubin
Review of Scientific Instruments 75 (2004) 5079-5083
We describe the design and calibration of an external cryogenic blackbody calibrator used for the first two flights of the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The calibrator consists of a microwave absorber weakly coupled to a superfluid liquid helium bath. Half-wave corrugations viewed 30 deg off axis reduce the return loss below -35 dB. Ruthenium oxide resistive thermometers embedded within the absorber monitor the temperature across the face of the calibrator. The thermal calibration transfers the calibration of a reference thermometer to the flight thermometers using the flight thermometer readout system. Data taken near the superfluid transition in 8 independent calibrations 4 years apart agree within 0.3 mK, providing an independent verification of the thermometer calibration at temperatures near that of the cosmic microwave background.
http://arxiv.org/pdf/astro-ph/0402580v1.pdf
Publications: Microelectronics: Properties of thin-film SiO2: 1989
Measurements of the thermal conductivity of micrometer-thick films of silicon dioxide are reported for the first time. Results show that the thermal conductivity is much lower than the values reported for bulk specimens, decreases with increasing temperature, and decreases with decreasing film thickness. This means that heating effects may be much larger than expected in accelerated stress tests and in other cases where joule heating can be a concern.
Schafft, H.A. ; National Institutes of Standards & Technology, Gaithersburg, MD, USA ; Suehle, J.S. ; Mirel, P.G.A. Microelectronic Test Structures, 1989. ICMTS 1989. Proceedings of the 1989 International Conference on Date of Conference: 13-14 March 1989
Schafft, H.A. ; National Institutes of Standards & Technology, Gaithersburg, MD, USA ; Suehle, J.S. ; Mirel, P.G.A. Microelectronic Test Structures, 1989. ICMTS 1989. Proceedings of the 1989 International Conference on Date of Conference: 13-14 March 1989
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