1

Chemistry / Re: What are the white rings that form during the Beirut ammonium nitrate explosion?

« on: 06/08/2020 12:18:51 »

The first video had a white spiral BBC logo added at the start.
- But the white clouds behind the shockwave are real in all the videos.

Some other videos I have seen showed a fire in a fireworks warehouse. The people seeing the fireworks seemed to think this was quite entertaining - quite unlike the massive explosion that appeared to be triggered by the fireworks.

Chemists on TV tonight said that you have to get Ammonium Nitrate quite hot before it explodes - so fireworks should probably not be stored next to  Ammonium Nitrate!

2

Chemistry / Re: What are the white rings that form during the Beirut ammonium nitrate explosion?

« on: 06/08/2020 10:30:41 »

Looks like the white rings are added artwork to the video.
This BBC article has the video without the rings at the beginning.
https://www.bbc.co.uk/news/amp/world-middle-east-53656220?__twitter_impression=true

What are you on about?

The clouds are real.
It would be silly to add them.

They are present in all the videos, (about 8 seconds into the 2nd vid, for example) though they are clearer in some than in others.

They form because the air immediately behind the shockwave expands rapidly and cools, causing moisture to condense from the air.
You don't need an explosion to see the effect- it's part of what causes condensation trails behind aircraft.
https://en.wikipedia.org/wiki/Vapor_cone

The explosion is mainly NH4NO3 --> H2O + N2 + O2
 The O2 released reacts with any oxidisable impurities in the material which increases the heat released.
Some NO and NO2 are produced too
NO2 is brown, and you can see that in the cloud.

3

COVID-19 / Re: Could asymptomatic people have invisible organ damage?

« on: 04/08/2020 19:37:57 »

My understanding is that this may be possible. "asymptomatic" unfortunately doesn't strictly mean "no symptoms of the disease occurred," it means "no symptoms of the disease were recognized."

It took many weeks before people realized that "asymptomatic" individuals could be diagnosed by looking for loss of smell/taste, or "covid toes." (new symptoms were discovered)

There are anecdotes of individuals who are (otherwise) "asymptomatic," but developed blot clots, which then caused stroke. So I would imagine that there could be cases of individuals who are infected, don't present the "standard" fever/cough/malaise but could still sustain significant damage to liver or kidneys or what have you...

There is still so much we don't understand about this disease...

4

COVID-19 / Re: Do we know the dosage required to get a COVID infection?

« on: 29/07/2020 16:09:15 »

My hunch is that the prominent 5 day oscillation cycle

What 5 day oscillation?

Have a look at the daily infection graphs on this site. They all display a 5 dayish oscillation cycle.
https://www.worldometers.info/coronavirus/

It's a 7 day cycle, with peaks on Fridays. Most people will work through a low-grade infection and report sick at the end of the working week, with maybe another peak on Monday. Labs may back up their results but post them all on Friday to clear the deck for next week.

The deaths graph is odd, as that also peaks on Friday. Whilst recorded deaths peak on Mondays (because register offices are often closed at the weekend) recorded cause of death seems to peak at the end of the doctors' working week. 

As foir viral load, it's pretty obvious that the more you have, the more likely you are to infect someone else, and the morf you inhale, the more likely it is that some will penetrate your first line of defence and set up shop before the immune system gets into gear. The lack of early symptoms is interesting. It seems as if the innate immune system is very insensitive to the virus, so you can build up an overwhelming viral load before the adaptive system adapts, by which time the innate inflammatory response suddenly turns on as well, producing the excessive inflammation that can become fatal.     

5

COVID-19 / Re: Do we know the dosage required to get a COVID infection?

« on: 27/07/2020 02:26:39 »

https://www.sciencemediacentre.org/expert-reaction-to-questions-about-covid-19-and-viral-load/

6

Physiology & Medicine / Re: What is the best form of calcium supplementation for osteoporosis?

« on: 17/07/2020 21:14:14 »

For each exercise you simply push, pull, lift or whatever against a spring and a strain gauge for about 30 seconds, so the force you exert is up to you and is recorded. The exercises are designed to stress the skeleton rather than work the muscles, hence there is very little movement (around a centimeter or two) or repetition, unlike ordinary weight training. Natural self-competitiveness makes you want to at least repeat and preferably exceed your baseline at each visit, which generally happens, but the real target is to increase bone density, not muscle mass. And it seems to work.

7

Physics, Astronomy & Cosmology / Expansion of the universe - what is being measured?

« on: 17/07/2020 09:05:00 »

I was just reading about the Atacama Cosmology Telescope in Chile. Research is as active as ever in trying to determine the age of the universe and the rate at which the universe is expanding. Does this research measure the rate at which matter is travelling through the universe or measure the actual expansion of the fabric of the universe?

8

Chemistry / Re: What is that liquid in the video?

« on: 06/07/2020 06:10:06 »

Hot grease, it seems.

9

Physiology & Medicine / Re: What is the evidence for scar-healing treatments?

« on: 28/06/2020 09:40:34 »

All silicone products work to reduce the size and overall appearance of the scar. It will often help heal discoloration and the texture of the scar. They contain antioxidants that make the scar heal more effectively. They heal skin by adding moisture, oxygen, and hydration. Sheets work faster because you can leave them on all day under clothing.  Sheets can be worn overnight too.

Silicone sheets reduce redness, and itchiness of the scar. They come in many sizes and can fit almost any size scar. It is the safest method around.  Silicone sheets, tape, and gel are an effective say to heal scars after surgery. How to heal scars is easy with silicone gel products. This is one of the most effective scar treatments with the least side effects. Ask your doctor to recommend a brand like scarheal to aid with your recovery after surgery.

10

Technology / Re: Using ions to electrify space debris to slow down in earth's magnetic field

« on: 14/06/2020 23:38:15 »

Their are currently two competing methods for the clearing of space debris:

a) Physical orbital mitigation  see Clearspace and ESA and other companies.

b) Laser vaporizing of Space debris see Roscosmos. Patents have been filed by this organization with the European Patent Office. 

Professional translators warning:
========================
Great care should be exercised with Russian patents, as they are often poorly translated and claims made are without peer to peer approval.

11

Physics, Astronomy & Cosmology / Re: Is this gyroscopic antigravity?

« on: 01/06/2020 08:24:44 »

Eric Laithwaite was an interesting character. His work on electromagnetic suspension and motor systems was inspirational and timely, and he contributed some great ideas in the aerodynamics of buildings, but his lack of understanding of the conservation of angular momentum was baffling.

Interestingly, Eric Braithwaite also served in the RAF and studied physics, but became a schoolteacher, author and later a lecturer in English, not engineering.

The odd thing is that Laithwaite's RAF career was as a test engineer on autopilots, so he should have understood the theory of gyroscopes pretty well.

12

Physics, Astronomy & Cosmology / Re: Is this gyroscopic antigravity?

« on: 01/06/2020 06:16:37 »

Wiki page on Eric Braithwaite says:
"In his lecture before the Royal Institution he claimed that gyroscopes weigh less when spinning and, to demonstrate this, he showed that he could lift a spinning gyroscope mounted on the end of a rod easily with one hand but could not do so when the gyroscope was not spinning."
"In his 1974 lectures, Laithwaite suggested that Newton's laws of motion could not account for the behaviour of gyroscopes and Laithwaite suggested that they could be used as a means of reactionless propulsion."

The effect is easily demonstrated.  The spinning gyroscope (a wheel at the end of a long axle, lifted by the other end) has only weight, but if not spinning, torque must also be overcome, making it far more difficult to lift despite no difference in weight.  I doubt that a professor has that poor of an understanding of simple gyroscopic effects, so my impression is more of somebody claiming amazing feats to the gullible when it is just ordinary (Newtonian) physics going on.
I think I can find a link to a video of somebody doing this, discussed in another thread.

Not sure if this has anything to do with the OP.  On the ISS, the device would have no weight in the first place and would not precess, and has no concept of being 'lifted'. I don't see any mention of 'jumping' in any descriptions in the searches I ran.

13

Physics, Astronomy & Cosmology / Re: Is this gyroscopic antigravity?

« on: 01/06/2020 05:55:38 »

I found an article by NASA speaking about Laithwaite's idea. Scroll down to the section titled "Gyroscopic Antigravity": https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070004897.pdf

So far, I haven't found any information about a test of such a device aboard the ISS.

14

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 23:43:59 »

How about the radiation fields ?

The Sun's radiation has been used experimentally to move spacecraft, with a solar sail:
https://en.wikipedia.org/wiki/Solar_sail

Cosmic rays carry a massive momentum for nucleus. However, they arrive randomly from all directions, so they are not very useful for controlled propulsion.

LEO (Low Earth Orbit) is shielded from most of the Sun's Solar wind by the Earth's magnetosphere. What remains is mostly low-density charged particles spiraling down the Earth's magnetic field lines towards the north & south magnetic poles. Since this doesn't provide a very consistent thrust to a satellite in orbit, it's hard to see how to use this for propulsion.
See: https://en.wikipedia.org/wiki/Magnetosphere#Earth's_magnetosphere

15

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 22:35:24 »

I assume the energy you are hoping to create is due to your movement through the field ? This is a law of physics that escapes me at the minute but it had something to do with an airplane oving through the earths magnetic field and how much charge it would create its also constrained by energy conservation, basically you have to put energy in to the movement to get the electrical energy out.

Is it possible to use the earth's magnetic field to move around in space, or even take off from earth?

The earth’s magnetic field is very weak compared to the force required to move a spaceship. It can move a magnetised needle on a low friction support, but anything heavier like a bar magnet on a desk doesn’t move. Also even a weak bar magnet will easily overpower the earth’s field and influence a compass needle
As we get further from earth the earth’s magnetic field gets weaker, but a magnet will still be able to align along the field see

Notice how the magnet is stronger than the earth’s magnetic field.

How about the radiation fields ?

16

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 11:48:34 »

Large satellites use gyroscopes to maintain their orientation in space.

Gyroscopes are a bit too heavy for tiny satellites, so small satellites in Low-Earth orbit generate a magnetic field, and work off the Earth's magnetic field (as illustrated by the astronaut).
- Unfortuantely, this won't give you propulsion, only orientation.
See: https://en.wikipedia.org/wiki/Magnetorquer
https://en.wikipedia.org/wiki/Control_moment_gyroscope

Is it possible to use the earth's magnetic field to move around in space

Yes, in a very limited way.

It has been suggested as a way to de-orbit old satellites in Low Earth Orbit, or to boost the orbit of satellites in Low-Earth Orbit, or even generate electricity in Low-Earth Orbit, using an electrodynamic tether.
- This has been tested from the Space Shuttle
- You don't get something for nothing; if you generate electricity, you lose orbital height; if you want to gain orbital height, you have to inject electricity
- I think the main concern is that a (say) 10km tether hanging in space would be a major obstacle to satellites in passing orbits. I think it would destroy too many satellites, and increase space shrapnel.
See: https://en.wikipedia.org/wiki/Space_tether

Is it possible to use the earth's magnetic field to ...take off from earth?

I can't see how this is possible - the Earth's magnetic field is too weak.

It is conceivable that a superconducting accelerator built in a vacuum tunnel up the side of a high mountain could launch satellites into orbit - but the mountain would need to be very high to get above most of Earth's atmosphere.

17

Technology / Re: Altering orbits using earth's magnetic field or generated fields from earth?

« on: 27/05/2020 07:10:12 »

Is it possible to use the earth's magnetic field to move around in space, or even take off from earth?

The earth’s magnetic field is very weak compared to the force required to move a spaceship. It can move a magnetised needle on a low friction support, but anything heavier like a bar magnet on a desk doesn’t move. Also even a weak bar magnet will easily overpower the earth’s field and influence a compass needle
As we get further from earth the earth’s magnetic field gets weaker, but a magnet will still be able to align along the field see

Notice how the magnet is stronger than the earth’s magnetic field.

18

COVID-19 / Re: Could the infection rate be significantly underestimated?

« on: 17/04/2020 16:19:00 »

It's highly likely that infection rates are higher than we thought or think. Partick Vallance (UK chief scientific officer) suggested at one point that the ratio of deaths to actual infections might be close to 1:1000; so with 10,000 plus deaths there may well have been 10 million cases in the UK already.

What will solve this is widescale serological testing. Once we can test the UK at scale for antibody to infection and discover how many people have really had it, we can refine and reinforce our models and control measures accordingly. Personally, I suspect that there has been considerable widescale spread in the community already.

19

COVID-19 / Re: Is viral pneumonia result of immune reaction or viral damage?

« on: 07/03/2020 22:36:19 »

Both.

Viruses are obligatory intracellular parasites, meaning that they rely on invading and hijacking our cells in order to replicate. When they do so, they usually compromise the cell, leading to its ultimate destruction. As such, viral infection leads directly to tissue damage; if this is in the lung, that's a pneumonia.

At the same time, viral replication in cells leads to the production of various cellular alarm signals called cytokines. These attract the immune system, which then sets about destroying virally-infected cells; but in the process it usually also causes bystander damage to adjacent healthy tissue. This is a pneumonitis.

Both phenomena will occur at the same time; usually the degree of damage is low, but in some cases it can be severe. The evidence we have is that the 1918 Spanish flu pandemic strain (H1N1) provoked just this sort of immune overdrive, leading to catastrophic lung damage, especially in people with healthy immune systems. This is, we believe, the main cause of death in these people.

20

Physics, Astronomy & Cosmology / Re: How microwave superheats water?

« on: 27/01/2020 09:20:58 »

Superheated water can be produced in pure water, in clean vessels without nucleation sites, and as long as it is not too agitated.
- So mechanical heating/stirring would not be a good way to do it
- Pure water is not very magnetic, so magnetic heating would not work so well
- Pure water is not very conductive, so heating by electric conduction would not work so well
- Inductive heating of a clean metal vessel could work
- Infra-red radiation (eg inside an oven) would work well

The information I gathered around this problem doesn't indicate the use of pure water.

The water can be regular drinking water but should not
contain many undissolved particles. It can be heated in any
domestic microwave oven; a research-grade microwave oven
such as used by Kennedy (1) to determine the enthalpy of
vaporization of liquids is unnecessary here. The recommended
heating vessel is a glass teapot sold to be used in the microwave
oven (no metal parts). Using such a teapot generally has several
advantages: its walls have relatively few nucleation
sites for bubble formation, yet enough to put a reasonable
limit on superheating; it has a plastic lid to prevent boiling
water from splashing out of it; and it has a plastic handle so
that it can easily be removed from the microwave oven once the
water is boiling.

Erné, B.H. & Snetsinger, P. (2000). Thermodynamics of water superheated in the microwave oven. Journal of Chemical Education
77(10), 1309-1310. doi: 10.1021/ed077p1309

And this is a comment by someone who can reproduce the phenomenon reliably.

Steven Spielman, PhD in Applied Physics; optical properties of solids
Updated Mar 4, 2019
I was able to accomplish superheating without much effort. I heated water in a small glass bowl, in a microwave oven. Before it reached boiling, tiny air bubbles adhered to the glass, the result of dissolved gases coming out of solution. When the boiling point was reached, (presuming here) water vapor entered these bubbles without bound and they grew quickly. The water boiled normally.

I shut off the microwave for a few seconds, and the boiling stopped. Then I turned it on again. The dissolved gases have already been driven out of the water, so there would have been no air bubbles to get things started. The water just sat there quietly for 10 seconds or so. Then there was a “PUNF!” sound. I opened the oven to find the bowl mostly empty and the walls and ceiling wet.

So, to avoid it, don’t microwave water (including coffee, etc.) which has recently boiled. Keep your face away when you first disturb it with a spoon or sugar.

https://www.quora.com/How-likely-and-how-dangerous-is-superheated-water-in-a-microwave-oven-and-what-everyday-precautions-should-be-used-to-avoid-injury