What is Nuclei: Definition and 141 Discussions

The raphe nuclei (Greek: ῥαφή, "seam") are a moderate-size cluster of nuclei found in the brain stem. They have 5-HT1 receptors which are coupled with Gi/Go-protein-inhibiting adenyl cyclase. They function as autoreceptors in the brain and decrease the release of serotonin. The anxiolytic drug Buspirone acts as partial agonist against these receptors. Selective serotonin reuptake inhibitor (SSRI) antidepressants are believed to act in these nuclei, as well as at their targets.

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  1. V

    Most stable nuclei are magnetic

    Hi, I'm in my last year of school and part of my A-Level is on nuclear physics. We've recently studied binding energy and I noticed that the elements with the highest binding energy per nucleon (the most stable nuclei) are magnetic - iron, cobalt and nickel. Are binding energy and magnetism...
  2. K

    Exploring Decrease in Binding Energy per Nucleon in Heavy Nuclei Like U-235

    Homework Statement . Why does the binding energy per nucleon decrease with increase in mass number for heavy nuclei like 235 U? Homework Equations The loss in energy of the nucleons when they move from an unbound state to a bound state is the binding...
  3. A

    Problem For Structure of Nuclei - Enigmatic

    Problem For Structure of Nuclei -- Enigmatic ! Question :- calculate the distance of closest apprach for a head on collision between 5.30Mev alpha particle and nucleus of a copper atom? Answer The distance of closest approach is given by...
  4. P

    How to prove N=1.5Z for heavy nuclei?

    Hi, there. I was trying to prove a relation about the most stable situtation for a nucleus. According to the semiempirical mass formula, the less mass a nuclei has, the most binding energy has and, of course, the most stable is. I followed the "liquid drop model" (Weizsacker) for the binding...
  5. T

    Exploring the Spherical Shape of Nuclei and Resources for Further Research

    Is the notion of spherical shape of nuclei well proven by experiment? Could someone please direct me to a relevant source?
  6. B

    Relativistic collision of Au nuclei - why is this wrong?

    Homework Statement The RHIC at Brookhaven is colliding fully ionized gold nuclei accelerated to an energy of 200 GeV per nucleon. Each Au nucleus contains 197 nucleons. a) what is the speed of each Au nucleus just before collision? b) What is the momentum of each at that instant in time...
  7. R

    Question about electrons and nuclei

    I had some questions about this too. I also asked it on a different folder, but here it is: I'm hoping someone has a good analogy or way to explain this, which I understand in terms learning the words, but I don't have an intuitive understanding of it. Why don't electrons fly into the nucleus...
  8. B

    How many Coulombs of positive charge are in 1.0 mol of O2 gas?

    Homework Statement Suppose you have 1.0 mol of O2 gas. How many Coulombs of positive charge are in the atomic nuclei of this gas? Homework Equations I assume you would use Q=ne with Avogadro's number... The Attempt at a Solution 1 mol O2/ 6.23 x 10^23 * 8 protons * 1.60 x 10^-19
  9. K

    Electron Orbits and Nuclei 2- Rotation vs Orbital Motion

    1-is electron orbit about the nucleus ? 2-is there is different between rotation and orbit? thanks in advance
  10. A

    How does a system consisting of two nuclei have rotational symmetry?

    I don't see it. Can someone explain? The Wikipedia article (http://en.wikipedia.org/wiki/Rotational_symmetry) defines an object with rotational symmetry as an object that looks the same after a certain amount of rotation. But this seems vacuous; doesn't *everything* look the same after a...
  11. K

    Nuclear vs Hadron Mass: Exploring the Paradox

    independently these two points make sense but when you put them together it seems as if they should be consistent: hadrons express the energy that holds them together as mass and the boson that expresses the force is massless; a portion of a nucleus's mass is expressed as energy - the energy...
  12. N

    Neutron capture by light nuclei

    I have a decent understanding of neutron-induced reactions in heavy nuclei (fission, capture), but less so when light nuclei are involved. I do know of Li6 + n --> He4 + T and the Li7 equivalent. Those reactions are more like nucleus splitting (fission). My question is: do neutron capture...
  13. O

    Neutron-Only Nuclei: Stability & Forces

    Since both neutrons and protons feel the attractive strong interaction, and only protons feel the repulsive coulomb interaction, shouldn't 'nuclei' made of neutrons and no protons, be more stable than nuclei with roughly equal numbers of protons and neutrons? Or am I missing something here...
  14. B

    Hartree fock calculation in nuclei

    Homework Statement I need to solve these problems. Please help!: 1) Obtein the binding energies of 4He and 18O in the Hartree-Fock aproximmation. Use as variational space three oscillator shells for every occupied orbit. Don't use the spin-orbit coupling term. 2) Calculate (using...
  15. B

    Nuclei Single-particles Harmonic Oscillator Potential

    I am looking into the calculations of a harmonic oscillator potential for nuclei single-particles. The information I am looking at is at: http://en.wikipedia.org/wiki/Shell_model the specific section “Deformed harmonic oscillator approximated model” The specific question is, I don’t...
  16. B

    Calculating Nuclei Shell Energy Levels: No Bra-Ket Math Needed

    In the nuclei Shell Model I understand the nomenclature for the shell sequence but I don’t know how to calculate the respective energy levels for each shell. For example how do you calculate the energy level for 1g(7/2) or 3d(5/2) Pointing me to an online reference will also be...
  17. A

    Presentaion about the Nuclei, need materials?

    Hello, I am a physics master student and I have to present a talk about The Nuclei(its constituents, models, decays and radiation). I am searching the internet about useful graphics and materials, it seems to me hard to get appropriate ones! please post any web links that may help...
  18. E

    P+7Li->4He+4He energy of He nuclei

    Homework Statement p+^{7}Li \rightarrow ^{4}He +^{4}He Mass of 7Li = 6533.8 MeV/c^2 Calculate the kinetic energy of each helium nucleus if the incident proton has nearly zero kinetic energy. Answer: 8.68MeV Homework Equations E_{total}=\frac{mc^{2}}{\sqrt{1-(\frac{v}{c})^2}} The Attempt...
  19. S

    Reactions of captured muons with nuclei

    I read many years ago that muons captured by nuclei with Z>10 react with these nuclei faster than their simple decay. In other words, such reactions as muon + Fe-56 --> Mn-56 + muon-neutrino are faster than the simple decay of the muon to electron, muon-neutrino and electron-antineutrino. I...
  20. M

    Atomic Nuclei: Liquid, Solid, Charged - Explained

    how can you explain atomic nuclei. liquid, charged, solid what? and there are some words about nuclear radius rn, rp and rc. what is the meaning of these words. all these data are experimental results or calculated. one is "atomic data and nuclear data tables, vol 71, no. 1, 1999, G.A. Salazar...
  21. D

    How Do I Identify the Nuclei Wall and Two Major Types of Fungi?

    please help me... I can't find the "NUCLEI WALL" it says I must decribe the structure from the fungi and Include the nuclei wall but I can not find it anywhere as well not on the INternet or on books... Maybe someone could helpp me... And the other question is I must Include the...
  22. Amith2006

    Tracing the U(235,92) + Neutron Process to Final Stable Nuclei

    Homework Statement 1) In a sequential process, U(235,92) plus a neutron forms the compound nucleus [U(236,92)]* which then fissions; the fissions then produces decays. If the initial fission fragments are Ba(143,56) and Kr(90,36), illustrate a process leading to the final stable nuclei...
  23. A

    How do you determine the charge of nuclei?

    I have a few questions about nuclear physics: How do you determine the charge of nuclei? Isn't it always positive? Please tell me what equations/concepts I need to know for these objectives: 1. Use conservation of mass number and charge to complete nuclear reactions. 2. Determine the...
  24. S

    Probing Atomic Nuclei with Electron Scattering.

    Homework Statement To study the structure of the lead nucleus, electrons are fired at a lead target. Some of the electrons actually enter the nuclei of the target, and the deflection of these electrons is measured. The deflection is caused by the charge of the nucleus, which is distributed...
  25. B

    So the top quark is pure mass, with no internal structure, as heavy as a gold nuclei?

    The gold nucleus has an atomic mass of 197 with 79 protons and 118N and 79 electrons. The top quark has about the same mass, but no internal structure. It's just a particle with pure mass. Why would a structure of pure mass and nothing internal decay?
  26. M

    Estimating Radii of Carbon & Oxygen Nuclei with Data

    This is supposed to be an easy question, but I appear to be slightly lost. Can anyone give me a hint on what to do here? when waves of wavelength lamda are diffracted by a circular disc of diameter D the first minimum in the intensity of the scattered waves occurs at a scattering angle z...
  27. K

    Verifying Proton Removal from Sn and Sb Nuclei

    Hi can anybody help me on this I really need it. The nuclide Sn has a filled proton shell, 50 being on one of the magic nucleon number. Sb has an extra proton outside this shell to make 51. According to the shell model, extra proton should be easier to remove than a proton from the filled...
  28. A

    Two Protons Colliding- Stable Nuclei?

    Hi, I'm new to this forum, so I'm sorry if I've posted this in he wrong catergory. Anyway, I'm studying AS physics at the moment and my teacher was giving the class some lessons about the strong nuclear force and electrostatic repulsion of nucleons making the nucleus stable. To get to the...
  29. S

    Does Weak Nuclear Force Run Radiation?

    Weak nuclear force runs radiation right? as far as i know it is because of quantum tunneling that particles can get out. if so, then does it follow the idea that if i watch it, it doesn't happen? for example shrodingers cat, if he watched the isotope, then is there a 0% chance that he dies?
  30. Y

    Experimental methods for measuring the size of nuclei

    Hello all. I am trying to work through my problem sheets and I need some help from you guys.. I am trying to find out experimental methods to measure the size of the nuclei.. Thx so much K
  31. S

    Charge on Nuclei of Mg, Ne, K^+, S^2-

    I've got this following question which I don't really get: What is the charge on the nucleus of each of the following? (assuming they are neutral) a) Mg b) Ne c) K^+ d) S^2- What I don't understand is the definition of "charge on the nucleus" I am assuming that only protons have...
  32. W

    Fermi Interaction of Electrons with Nuclei

    Fermi Contact Interaction of Electrons with Nuclei About this interaction, is it the spins of nuclei which interact with the spins of electrons? So, if I draw the magnetic field line from the left nucleus via the pair of e- to the right nucleus and there is not anti-parallel field against...
  33. S

    Unveiling the Nuclear Force Acting on Atoms' Nuclei

    How do we determine the magnitude of the nuclear force acting on the nucleus of an atom?
  34. D

    Can We Find DNA in Blood Without Red Blood Cell Nuclei?

    If red blood cells don't have nuclei, then does this mean we can't find DNA in blood? Thanks
  35. wasteofo2

    What's in the space between atoms, or between nuclei and electrons?

    Is it known what's between atoms, or between the nuclei of atoms and their electrons? There's a great deal of space (relative to the size of the particles) between the electrons of an atom and it's nuclei, so are there some particles in those spaces, or is it essentially a vacuum? Thanks...
  36. C

    Radioactiviy - # of unstable nuclei after 28 hours

    I'm having trouble working out how to calculate the number of unstable nuclei remaining in a sample after 28 hours, the answer is 10 but I have no idea how its done, any help would be greatly appreciated. "If a sample of radioactive material initially has 3.7 x 10(^7) unstable nuclei, how...
  37. C

    Simple Measurement of Atomic Nuclei Radii

    Okay, we have a graph that shows how v.high energy electrons are diffracted by atomic nuclei and the first minimum is shown to be at approximately 51 degrees for carbon-12 with energy 420MeV. To calculate the nuclear radii I decided to use sin(theta)= 1.22lambda/d and rearranged this so d was...
  38. J

    What is the source of gravitational repulsion in certain cases?

    i was wondering this if the nuclear force overcomes the electromagnetic force in the nucleus, then what prevents the nuclei for colapse itself i read in somewhere this " the nuclear force has a repulsive core which prevents the nuclei from collapsing in on themselves" what is this...
  39. D

    Exploring Active Galactic Nuclei: A Comprehensive Guide for Beginners

    Can anyone inform me as to what an "active galactic nuclei" is? Thanks a lot!
  40. jimmy p

    Radioactive Nuclei: Stability & Effects of Size

    What properties of nuclei make them radioactive? I know it is mainly to do with stability of the nucleus, but are there any other reasons? Why are elements with smaller nuclei less radioactive than elements with larger nuclei?
  41. L

    New Geometrical Polar-Ring Solution for Magic Numbered Nuclei

    New Geometrical Polar-Ring Solution for Magic Numbered Nuclei. It is well known that if the neutron- or proton number within atomic nuclei have the following quantities (2, 8, 20, 28, 50, 82 and 126: the magic numbers), then the atoms are showing a more than average stability. As an example...
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