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  1. 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
  2. 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...
  3. 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...
  4. 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...
  5. 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...
  6. 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...?)...
  7. 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...
  8. 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...
  9. 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)
  10. 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.
  11. 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...
  12. ORF

    Why does this ant react like this?

    Hello This is the video: Question: why does the ant seem to be trapped by the ink circle? Thank you for your time. Regards, ORF
  13. ORF

    B Is there any macroscopic example for the "mass excess"?

    Hello In nuclear physics, the mass excess is caused by the nuclear binding energy. Question: is there any macroscopic example where the "mass excess" is non-negligible? Thank you for your time. Regards.
  14. ORF

    C/++/# Easy way of counting # processeses running?

    hello I needed to count the number of processes (with the same name). I found that this bash script works, #!/bin/bash exit $(ps cax | grep firefox | wc -l); and the exit value can be caught by this code #include <stdlib.h> // sytem #include <iostream> // std::cout, std::endl int main() {...
  15. ORF

    How surface tension is measured for molten metals?

    Hello How the surface tension is measured for molten metals? I have heard about the sessile drop, but it seems to be a very inaccurate method... Thank you for your time. Regards.
  16. ORF

    C/++/# How to check if a list of numbers is random?

    Hello I have used a random number generator to create a list of uniformly random numbers, between 0 and 1. The usual check that I do is sorting the list, and histograming the difference between the following and the previous one. The shape of the histogram should follow an negative...
  17. ORF

    Medical Why doesn't the intestine digest itself?

    Hello I have read this article about why doesn't the stomach digest itself https://www.scientificamerican.com/article/why-dont-our-digestive-ac/ but also during the digestion along the small intestine, there are enzymes. How does the small intestine defend against these enzymes? ( I suppose...
  18. ORF

    Misc. DIY muon detector -- Is it really working?

    Hello I found this video on YouTube, It seems that most of the counts are noise of the PMT... Thank you for your time. Regards.
  19. ORF

    A Gamma detection -- Cherenkov radiation in gamma-scintillator interaction

    Hello During a simulation of light in gamma-scintillator interaction, it seems that there are a lot of Cerenkov photons. I don't know their contribution to the final intensity (it will need a long time to compute it). The textbooks usually say that the gamma ray will produce secondary...
  20. ORF

    Zoology: How electroejaculation works?

    Hello I found some webs, but I would like to know a bit more https://en.wikipedia.org/wiki/Electroejaculation http://www.ivf-infertility.com/ivf/ejaculation.php "is to directly stimulate the seminal vesicles." I don't know how exactly works in "natural conditions", but it seems to me that the...
  21. ORF

    Biology: Does radioactivity help fungi to grow?

    Hello Does radioactivity help fungi to grow? The article is 10 years old, I do not know if there is something newer... https://www.scientificamerican.com/article/radiation-helps-fungi-grow/ Thank you for your time. Regards, ORF
  22. ORF

    Biology: Evolution: General selection rules?

    Hello In evolution, the archetype rule is the "natural selection" rule. Are the other selection rules? (technological selection rules, cultural rules, etc) Thank you for your time. Regards, ORF
  23. ORF

    C/++/# What are the "debugging symbols"?

    Hello What are the "debugging symbols" ? I have a naive idea about what the debugging symbols are, but based only in my short experience: for me, they are a kind of flags that can be read during the execution of the program, so you can track the execution. I have also discovered that if you...
  24. ORF

    Zoology -- How a mosquito's CO2 detection system works?

    Hello How mosquito CO2 detection system works? I found that the detection is made by npa neurons, but nothing is said about how the detection occurs (so, CO2 enters the neuron, and what happen next?) https://www.nih.gov/news-events/nih-research-matters/how-mosquitoes-detect-people Thank you...
  25. ORF

    Medical Why polyphenols make caffeine (from tea) work slower?

    Hello Why polyphenols make caffeine (from tea) work slower than caffeine from coffee? Thank you for your time. Regards, ORF
  26. ORF

    Detailed history about the discovery of "isotopes"?

    Hello I would like to know more about the history of the discovery of the isotopes, what there was before, and the short term impact on the chemistry and nuclear physics. Is this topic discussed in any book/review? Thank you for your time. Regards, ORF
  27. ORF

    Can a microorganism change the behavior of an animal?

    Hello. Can a microorganism change behavior of an animal? ( including humans). Thank you for your time. Regards, ORF
  28. ORF

    Biochemist -- Is isotope ratio unique for each trophic level?

    Hello As far as I know, the reaction velocity depends on the isotope ("kinetic isotope effect"). So, is the isotope ratio (for example, for Nitrogen or Carbon isotopes) dependent on the trophic level? Thank you for your time. Regards, Alvaro.
  29. ORF

    Best way of copying same data to several drives?

    Hello I would like to copy a huge amount of data (10-20TB) to 5-10 hdd (internal/external). I thought about using the usual "cp/rsync" utilities, but it will take a long time. After a quick search, I found this unix utility...
  30. ORF

    I Why uranium glass glows green if it's under UV light?

    Hello Why the uranium glass glows green if it's under UV light? The most accurate thing I have found it's a brief history of uranium glass: somewhere it's said the more uranium oxide you put in the glass, the more intense will be the green light when exposed to UV light. Thank you for your...
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