Carl Fredrik Ahl

14 hours ago, swansont said:

You should be able to google this, but...
https://www.systechillinois.com/en/support/technologies/electrochemical-sensor

Any gas molecule will absorb light that's resonant with a transition in that molecule; the electron energy states are quantized, so there is a specific energy difference between allowed states. Light that has that amount of energy is likely to be absorbed. For CO2, there are several transitions in the infrared, which are particularly well-known because it's why CO2 is a greenhouse has. So you pick one of the transitions, probably one that does not correspond to where water also absorbs, and use that the detect how much CO2 is present.

Thx for the answer. I looked on the link that you gave me, but I don't understand why it's not enough to only use the lead anode that get oxidesed.

So when the sensor have sent out the infrared and the C02 absorbs it, how does it get the information back? And how does it know how much C02 is in the air by doing so?

On 11/26/2018 at 4:50 PM, swansont said:

"Consume" in this case is having the molecule in question undergo a chemical reaction. It's done in a fuel cell, and there is a current associated with the reaction, similar to a battery reaction. the materials, and the reactions, are designed to be specific to the molecule. The fuel for the O2 sensor does not react to CO, and vice-versa.

The CO2 sensor is based on attenuation of IR light. CO2 has certain absorption bands in the IR. If you have a dual detector, you can compare an attenuated signal with an unattenuated one, and the loss is proportional to the CO2 concentration.

 

 

Thx for the answer, can you plz explain how this fuel cell works more specific and how the co2 absorption bands works more specific.

Hi,

I know that indoor air quality sensors works by measuring the amount of oxygen, carbon monoxide and carbon dioxide. I know that oxygen and carbon monoxide is measured by consuming it and get the electric current from that consumption to see the quantity of the gases and that carbon dioxide is measured with an infrared sensor.

I wonder how the sensor can consume oxygen and carbon monoxide and then get the electric current. I also wonder how the infrared sensor gets the amount of carbon dioxide. Does it calculate how much infrared light is reflectes back to the sensor?

17 hours ago, Janus said:

A nuclear fission reaction doesn't occur by one atom at a time.   First fission event produces 2 neutrons (or sometimes 3). Each of these neutrons go on to induce fission in two other atoms.   Each of these atoms produce 2 neutrons each, so now you have 4 free neutrons,   each capable  of inducing fission in a nucleus.

So it goes something like this:

1 atom produces 2 neutrons leading to

2 atoms producing 4 neutrons (2 each) leading to

4 atoms producing 8 neutrons, leading to

8 atoms producing 16 neutrons. etc.

 

Thanks for the answer!, now I understand

1 hour ago, swansont said:

Thermal fission of U-235 releases 2.43 neutrons, on average. As Sensei has implied, there are a number of possibilities for the reaction. Some give 3 neutrons or more. But they don't "make it" do that. U-235 is used because that's how it behaves. If it didn't, they would use something else.

edit: Pu-239, for example, yields ~2.87 neutrons per fission. U-233 yields ~2.48
https://www.nrc.gov/docs/ML1214/ML12142A078.pdf

Ok, does this mean that the initial neutron has enough kinetic energy to get two neutrons out of the first uranium and the two neutrons from the first uranium has enough kinetic energy to get three neutrons out of the second uranium and so on?

16 hours ago, Janus said:

While spontaneous fission is always occurring and in turn producing some induced fission reactions,   This isn't enough to cause a chain reaction if you don't have enough uranium 235 contained in a small enough region. For pure U 235, this  requires a sphere  52 kg in mass.   With a smaller amount, too many of the produced neutrons make their way out of the sphere without encountering a nucleus.¹   If you break the 52 kg into small pieces and separate them this has the same effect, it allows for more neutrons to escape without inducing a reaction.

Bring the pieces suddenly together and you have a critical mass that will produce your nuclear explosion. ²

 

¹ you can get away with using less if you surround the uranium with a neutron reflector which bounces the neutrons back through the mass, giving them another chance to interact with a nucleus.

² This presents its own problems.   As the pieces are brought closer together, the rate of induced fission events increases.  This creates an increasing energy output from the Uranium.  If they aren't brought together properly, or fast enough, this release of energy can be enough to blow the pieces apart from each other before they can get close enough to form that fully critical mass and produce the explosive fission event.   The bomb will fizzle out.   This type of bomb has to be designed properly so that the critical mass is formed before the individual pieces are blown apart again.  It's not a matter of keeping the bomb from exploding, it's getting it to explode properly.

Thx for the answer! I also wonder how they make it that the first uranium shoots out 2 neutrons and the second 3 neutrons and the third 4 neutrons and so on. How do they do that? I know it's necessary to hit more and more uranium and get the donimo effect. I just don't know how it works.

17 minutes ago, swansont said:

By virtue of being hot, the particles have enough energy to overcome the Coulomb barrier, i.e. electrostatic repulsion (or get close enough for quantum tunneling to be likely), and once that happens, the nuclear force of attraction is present, allowing the particles to fuse.

Thx for the answer. But I still wonder why they want to fuse, what benefits are there?

1 hour ago, Sensei said:

Tritium and Deuterium fusion reaction:

31H+21H→42He+n0+17.6MeV

alternative form:

T+D→42He+n0+17.6MeV

Tritium can fuse with other Tritium and release 10.446 MeV:

31H+31H→52He+n0+10.446MeV

Helium-5 is unstable isotope of Helium, and has only one decay mode via neutron emission:

52He→42He+n0+887keV

 

Free neutrons will be captured by Uranium-235, Lithium-6 or other fissile element.

63Li+n0→31H+42He+4.8MeV

alternative form:

63Li+n0→T+42He+4.8MeV

As always, kinetic energy of newly created particles (the lighter particle takes more energy), and gamma photons.

Thx for the answer. Can you please explain more basic why the hydrogen atoms wanna fuse together to be helium atoms instead of giving the formulas?

So kinetic energy is released, does this mean that the helium atom willl get that kinetic energy and move very fast, or will the surrounding atoms move fast or both? I'm don't know much about this, but I'm curious.

14 hours ago, StringJunky said:

Yes.

Why will hydrogen fuse together to form helium? How do they get attracted to each other just because it gets very hot and how (in what form) is the energy released when they fuse?

7 hours ago, Janus said:

I answered that in the post.  Not all instances of U 235 fission needs to be induced by absorbing a neutron.  One of the ways Uranium 235 can decay is to spontaneously undergo fission. It not the most likely way, but  you have some 2.5e21 Atoms per gram of Uranium. Even with nuclear fuel only enriched to 5% U 235,  you still are left with 1.25e20 nuclei;  a large enough number that even with only a 2e-7% chance of any given nuclei decaying by spontaneous fission, you are going to have a good number of nuclei undergoing such fission per minute.

Ok thanks for the answer. How do they prevent uranium from spontaneously undergo fission in an atomic bomb before they want the explosion?

13 hours ago, John Cuthber said:

If you are running a nuclear reactor then you can just wait for random "spontaneous fission" where the nucleus falls apart without being hit  by anything.

 

If you are making a nuclear bomb, then you don't have long enough to wait.
They rely on neutron sources based on things like mixtures of radium (which emits alpha particles) and Beryllium (which emits neutrons when hit by alpha particles.
And, if you want to make sure there are neutrons...

https://en.wikipedia.org/wiki/Startup_neutron_source

 

 

 

Thx for the answer. So they can use beryllium in atomic bombs to start the fission reaction of uranium. How do they isolate beyllium from the uranium before the moment that they want the explosion?

Hi,

I have heard that both fission and fusion take place in a hydrogen bomb. Is it true that the fission part is to make the fusion part very hot so that fusion can take place? Is it hydrogen atoms that will fuse together to helium atoms and this will make the big explosion?

38 minutes ago, Janus said:

Elements high on the periodic table contain lots of neutrons and protons in their nucleus.  This makes them less stable.  Uranium 235 is one of those elements.

Also, an excess of neutrons to protons can add to instability.    Most isotopes undergo simple radioactive decay (alpha or beta) to reach a more stable state.

Uranium 235 does this. It decays by alpha decay into Thorium 231.

But because of the particular arrangement of neutrons and protons in its nucleus, it can  also split into two smaller nuclei and some free neutrons by in an act called spontaneous fission instead.  This very rare event can happen all by itself.( All radioactive decay processes are statistical by nature, and some nuclei can take more than one route. You can never say with certainty which route a particular nuclei will take, only the odds of it following one or the other*. Spontaneous fission is very low on the probability list. ) 

If one of the free neutrons from this fission is absorbed by another U-235 nucleus, it briefly becomes a U-236 nucleus.  The U 236 nucleus is even more unstable and much more likely to decay by fission. This of course can lead to further induced fission in other nuclei.

So the introduction of the neutron makes an already unstable nucleus even more unstable. And the  fission inducing neutron could have been produced by the spontaneous (non-induced) fission of a U 235 Nucleus.

 

 

* Even with fission, there is a small chance of breaking into three smaller nuclei rather than two.

Thx for the answer.

47 minutes ago, Janus said:

Elements high on the periodic table contain lots of neutrons and protons in their nucleus.  This makes them less stable.  Uranium 235 is one of those elements.

Also, an excess of neutrons to protons can add to instability.    Most isotopes undergo simple radioactive decay (alpha or beta) to reach a more stable state.

Uranium 235 does this. It decays by alpha decay into Thorium 231.

But because of the particular arrangement of neutrons and protons in its nucleus, it can  also split into two smaller nuclei and some free neutrons by in an act called spontaneous fission instead.  This very rare event can happen all by itself.( All radioactive decay processes are statistical by nature, and some nuclei can take more than one route. You can never say with certainty which route a particular nuclei will take, only the odds of it following one or the other*. Spontaneous fission is very low on the probability list. ) 

If one of the free neutrons from this fission is absorbed by another U-235 nucleus, it briefly becomes a U-236 nucleus.  The U 236 nucleus is even more unstable and much more likely to decay by fission. This of course can lead to further induced fission in other nuclei.

So the introduction of the neutron makes an already unstable nucleus even more unstable. And the  fission inducing neutron could have been produced by the spontaneous (non-induced) fission of a U 235 Nucleus.

 

 

* Even with fission, there is a small chance of breaking into three smaller nuclei rather than two.

Thx for the answer. How is the initial neutron shot at the uranium?

Hi,

I wonder why uranium (don't remember what isotope) splits when a nuetron hits it. I also wonder how the initial neutron get shot at the first uranium.

6 hours ago, BabcockHall said:

Almost nothing of what you wrote is true.  Liver stores glycogen and can make glucose from it.  Glucagon is a hormone, and is not the same thing as glycogen.  Glucose and fructose have a complex relationship metabolically.  Do you have a copy of Nelson and Cox's biochemistry textbook or something equivalent?

Thx for the answer. No I do not.

6 hours ago, SamIam said:

Fructose metabolism in muscle differs little than that of glucose. Hexokinase witch converts glucose to G6P on entry into muscle cells, also phosphorylates fructose yielding F6P.

Thanks for the answer.

Hi,

I think I have heard that the liver can only store fructose and the muscles can only use  glucose (to make glucagon). Is this true? What happens then if the muscle needs energy and you only consume fructose? Will no glucagon get stored in the muscles then? I have also heard that fructose can get converted to glucose. Can someone please explain? I am confused.

Hi,

I have heard that when you have consumed protein, but no muscle cells (for example) need it, the protein is stored as fat. But if you excersie like an hour after you eat, will that protein get stored as fat because the muscles didn't need to repair then, or is it still in the blood ready for the muscles to repair after the excersie?

Hi,

Can someone plz give me a list of which proteins are used for energy, in what food you can consume them and which of the proteins give most energy. Can someone also give me a list of proteins used for muscle growth and the ones that are most efficient of those.

Thx for the info, yeah I forgot how it was.

Hi,

I don't understand how long carbohydrates last in the liver to be used up by the body. I know that the cells will take as much energy as they need when you have consumed carbohydrates, but let's say there are suger left over in the liver which will be stored as fat, HOW LONG WILL THE SUGAR STAY IN THE LIVER BEFORE IT'S STORED AS FAT? Maybe after a while you'r cells need more energy, but the sugars has already been stored as fat?

2 hours ago, Sensei said:

That's certainly not true..

Unsaturated fat differs from saturated fat that it has one or more C=C bond. Unsaturated fat HAS Hydrogen atoms. (at least) two less Hydrogen atoms than saturated form.

 

Oh ok, thx for the info. So what happens when you eat those fats?

Hi,

I know that there are a lot of different days in different food and that unsaturated fats doesn't have any hydrogen atoms but only carbon atoms and that saturated fats have both of them. What I wonder is that when you consume fat, say unsaturated fat for example, it will behave just like carbohydrates and get converted to glucose and used up by cells if the body needs energy and otherwise store it as fat? Or does it get stored as fat directly and then burned?

2 hours ago, fiveworlds said:

Do you have a voltmeter to check that the battery is still holding charge?

No, I don't but I'm giving up and I don't know how to delete this post, but thx.

12 hours ago, Sensei said:

Chemical properties changes. e.g. slightly different melting and boiling point temperatures. Mass of molecule is smaller by 2.016 u.

Google for "bromine water test unsaturated oils" to see e.g. movies or articles how to detect unsaturated fat.

https://en.wikipedia.org/wiki/Bromine_test

 

Ok, thx for the information. You say that the melting and boiling temperatures differs between them. But both types of fat will be stored in fat tissue, make you fat and cause triglycerides to accumulate in the blood? Is my understanding true?

Hi,

I wonder if the only difference between unsaturated fat (like in nuts for example) and saturated fat (like in cockies for example) is the amount of bonds in the fat regarding carbon molecules and hydrogen molecules and in that case, how can that matter?