Recent content by ORF

  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...
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