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  1. ORF

    Favorite Physical Sciences Podcasts?

    Hi, I would follow Jim Al-Khalili, nuclear physicist from Surrey University (UK). He has a program at BBC, and many documentaries and (audio)books. He explore many cutting-edge science topics, and some times you would need a bit of physics to follow...
  2. ORF

    CAMAC crate electronics - Where were/are they used?

    Hi, If you want to buy some old stuff, you may ask the main nuclear physics labs/facilities in your country, they can tell you if they are using them, or planning to get rid of some CAMAC crates/modules. If they have some old modules and they are not in use, maybe they can give them to you free...
  3. ORF

    I Microcanonical ensemble generalized pressure

    Hi, please, crosscheck that the partial derivative is for S and N constant https://de.wikipedia.org/wiki/Mikrokanonisches_Ensemble#Druck (sorry, it was the only wikipedia article with the pressure definition as partial derivative) Regards, ORF
  4. ORF

    B There's Gold in Them Neutron Stars - or - Maybe Not

    Hi, there are issues difficult to understand and explain in both sources. It is claimed that Neutron Star Mergers (NSM) are not the main source of r-process elements because of timing: there are r-process abundance pattern in metal-poor stars in the galactic halo, which are up to 12Gyears old...
  5. ORF

    I Why the alcohol thermometer is less precise than the mercury one?

    Hi, Why the alcohol thermometer is less precise than the mercury one? If I remember correctly, it is because the thermal expansion coefficient of alcohol is not constant, but I am not sure. Thank you for your time. Regards, ORF
  6. ORF

    B There's Gold in Them Neutron Stars - or - Maybe Not

    Hi, Their simulation has a number of assumptions... This does not come from pure simulations ;) https://www.nature.com/articles/s41586-019-1676-3 Regards, Alvaro.
  7. ORF

    I When is weak interaction a force?

    Hi, The range of the weak interaction is shorter than the size of an atom (although s-orbitals overlap the nucleus...) Regards, ORF
  8. ORF

    I Low-lying excited states in nuclei

    Hi, you can also compare with theoretical shell model calculations, and assign spin and parities from these models. Regards, ORF
  9. ORF

    A "Reversal" of Nuclear Decay in Beta Emitters

    Hi, this is the state-of-the-art theoretical framework of electron capture https://arxiv.org/pdf/nucl-th/0001018.pdf Converting a proton into a neutron, or viceversa, involves weak interaction. As its own name says, it is not likely to happen. Reaction rate is given by r = n1 * n2 * <sigma*v>...
  10. ORF

    Explain why Mo–95 & La–139 are more stable than U–235

    Hi, The Semiempirical Mass formula gives an idea of binding energy in nuclei. It treats the nuclei as fluid, so a number of terms are introduced: volume, surface tension, coulomb repulsion among protons, symmetry, and pairing neutron-proton...
  11. ORF

    Hubble's Law and Doppler Shift

    Hi, There are two different concepts: the Universe, and the observable universe ( a part of the Universe ). In a universe with constant Hubble parameter, light emitted at the present time by objects outside the Hubble limit would never be seen by an observer on Earth...
  12. ORF

    Is there a proof about angular momentum conservation?

    Hi, A more abstract (and fancy) proof is given by Noether's theorem: if your system is invariant under rotation, angular momentum is conserved https://en.wikipedia.org/wiki/Noether%27s_theorem#Applications Regards, ORF
  13. ORF

    Waves and vibrations on a string

    Hi, Here it is the solution to the last question: https://oyc.yale.edu/sites/default/files/Erratum-Wave%20energy_0.pdf I hope it helps. Regards, ORF
  14. ORF

    Lab Experiment: Estimate the error in these measurements of Ohm's law

    Hi, I have measured a set of V-I values, and I have to provide the value of the resistance. I have used ac and dc current. The circuit was quite simple: power supply -> ammeter -> resistance -> [power supply] wave generator -> ammeter -> resistance -> [wave generator] Voltage was measured...
  15. ORF

    Can a forest die?

    Summary: If a forest is scorched, after a while it will regrow(wont it?); but if it is periodically burnt to ashes, could it eventually die? (as a ecosystem) What is the time-scales in order to recover a forest after a blaze? Hello, If a forest is scorched, after a while it will regrow (wont...
  16. ORF

    Open science in Europe

    Hello all, in the near future, open science (open science != open access) will be real in Europe. It is a bit controversial, specially in some fields. What do you think about it? As far as I know, researchers in Astronomy exploit it successfully. But I am not sure about the impact of open...
  17. ORF

    Do carnivores have a higher proportion of light isotopes than plants?

    Hello, because of the "kinetic isotopic effect", https://en.m.wikipedia.org/wiki/Kinetic_isotope_effect can the ratio of the common isotopes of N, C, P, H, O, S determine the position of an individual in the food chain? (eg, have carnivore animals higher proportion of light isotopes than...
  18. ORF

    What limits the amount of renewable energy sources?

    Hello, I was told every country needs a constant electricity production source (like coal or nuclear powerplants), and up to some proportion, renewable sources (photovoltaics, hydro, wind turbines, etc). So, my question is: what limits the amount of renewable sources? (the grid, storage...?)...
  19. ORF

    How can KCl be enriched in 40K at home?

    Hello, I have pure KCl, but its natural radioactivity is low. I would like to increase it at least by a factor of 10. Is there any simple way (diy) for enriching the natural KCl in 40K? Alternatively, is there a compound with higher concentration of potassium (in volume) than KCl, and that you...
  20. ORF

    A Need help with the reaction of neutrons and electrons

    Hello, The interaction for case (1) is weak, because a charged lepton is turned into neutral lepton. So, the quantum numbers that must be conserved are electrical charge (ok), barionic number (ok), energy (ok?). Lets see angular momentum: J(n) = 1/2 J(e-)=1/2 J(D-)=3/2 J(ne)=1/2 The...
  21. ORF

    Why is iron added to the head of a match?

    Hello, The explanation for this, min 0:54 is that you have Fe2O3 in the match head, and after burning it, pure iron is obtained 2 Fe2O3 + 3 C -> 2 Fe + 3 CO2 I think the chemical explanation is fine, but I don't understand why Fe2O3 is added (as colorant, if the red phosphorus is already...
  22. ORF

    C/++/# Is std::bind reentrant?

    Hello, Thank you very much, that was the answer I needed! :D Cheers! ORF
  23. ORF

    C/++/# Is std::bind reentrant?

    Hello, but, if once it is initialized, you can not know the bound arguments... that is also reentrant? (probably I have a misconception of what reentrancy is) Thank you very much for your time. Regards, ORF
  24. ORF

    C/++/# Is std::bind reentrant?

    Hello, No, I'm not using recursion. I was told that std::bind is not reentrant because the bound (copied) arguments may not be retrievable. I didn't find any information about how to retrieve the bound arguments, and that is my question: is std::bind reentrant? (or, can you retrieve the...
  25. ORF

    C/++/# Is std::bind reentrant?

    Hello, I am a kind of noob... how can you retrieve the bound arguments from the returned object? http://www.cplusplus.com/reference/functional/bind/ Thank you for your time. Regards, ORF
  26. ORF

    I How many ion-pairs are there in normal conditions in the air?

    Hello, if the order of magnitude is 1e3 ions/cm3, it is fine: I expect a production of 1e6 ions/cm3/s (upper limit) from a weak source. Regards, ORF
  27. ORF

    C/++/# Is std::bind reentrant?

    Hello, is std::bind reentrant? If not, the bound values have to been stored somewhere? Thank you for your time. Regards, ORF https://en.wikipedia.org/wiki/Reentrancy_(computing)
  28. ORF

    I How many ion-pairs are there in normal conditions in the air?

    Hello, I would be interested in a rough estimation, the order of magnitude, rather than an exact reference number. The conditions would be: humidity: 90% no rain/snow/no clouds, no wind (inside lab), at sea level, north hemisphere, normal background ~100 nSv/h little of dust Well, you...
  29. ORF

    I How many ion-pairs are there in normal conditions in the air?

    Hello, I don't know how to compute that number, but probably is a kind of reference value... Q: How many ion-pairs are there in normal conditions* in the air? (This is not homework, it is just out of curiosity.) Thank you for your time. Regards, ORF * 1 atm, 300K.
  30. ORF

    C/++/# Question about input format file (for creating a net)

    Hello I am not sure about what should be the best format for a input text file. I think before start shooting in the dark, it's better to ask experienced people. The (C++) program has to create a net. The nodes will be defined in a input text file. For convenience, the net will be a bunch of...
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