Recent content by ORF

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...

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...

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

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...

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

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.

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

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

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>...

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...

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...

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

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

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...

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...