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.

View More On Wikipedia.org
Recent contents Top users
  1. F

    Beta Decay: Unstable Nuclei & Why It Occurs

    I've started studying physics at a basic level and I've ready that beta decay takes place when the number of neutrons exceed the number of protons in a nucleus. Why does this excess number of neutrons compared to protons make the nucleus unstable? Also, what does an unstable nucleus mean?
  2. G

    Reactant nuclei and product nuclei

    Homework Statement in the photo, the 23Na form 24Na Am i right? if i am right, the mass of 23Na should decraese , and mass of 24Na should increase. but why the solution provided is the mass of 24Na decreses and increases at the time of delta t ?? i can't understand Homework EquationsThe...
  3. S

    Calculating energy released due to fission of heavy nucleus into equal nuclei.,,

    Homework Statement There is this university exam question: Draw the nuclear binding energy curve and and show that energy is released when a heavy nucleus of A> 200 breaks up into two nearly equal fragments. Homework Equations See below. The Attempt at a Solution I found in an example in...
  4. T

    Wave Function_vibtrating nuclei

    Homework Statement The Ground state wave function governing the motion of a pair of vibrating nuclei looks like: wave function = wave (x) = (a/pi)1/4 e-ax2/2 where a = alpha = mu*w/(h bar), which is determined by mu = reduced mass of the pair where w = angular vibrational frequency ...So...
  5. Z

    Spin of 1p1n Nuclei: Theory & Explanation

    I am interested in the topic of the thread https://www.physicsforums.com/showthread.php?t=768539 ,especially for those unpair 1p1n case. As I know, for the simplest case deuteron, the Jπ (groundstate here and later) is 1+ but 0+. This is very different to the atomic physics case. For He...
  6. T

    What is the EMC effect and how does it challenge conventional nuclear physics?

    Hi Based on what I know (it might be wrong) properties of nuclei are calculated based on the different (simplified) models of the p and n "particles" (shells, droplets etc). I have 2 questions: 1. To what extent can we assume that n and p are "elementary" particles bound by residual strong...
  7. A

    Half and mean life of nuclei

    Homework Statement Radioactive nuclei are produced in an irradiated sample at the rate of 10 s-1. If the number in the sample builds up to a maximum of 1000, calculate the mean life and the half-life of the radioactive nuclei Can anyone advise on this one not sure how mean life is found...
  8. lonewolf219

    The number of nuclei in 1 gram of copper (Cu)

    ^{62}Cu is 61.932586 amu. I would like to know how many exposed nuclei are in 1.0 gram of ^{62}Cu. I have two calculations below, hopefully one of them is correct... Method 1. 1.0 gram ^{62}Cu x \frac{1 kg}{1000 g} x \frac{1 amu}{1.660566 x 10^{-27}kg} x \frac{1 mole ^{62}Cu}{61.932586...
  9. N

    Neutrinos incident on target - interaction with nucleons or nuclei?

    I came across a worked example question in a particle physics book this morning that had a beam of neutrinos of energy 2.3MeV incident on a lead target. The point of the question was calculating the thickness of lead needed to reduce the beam intensity by a certain fraction - and the solution...
  10. T

    Probing 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...
  11. U

    How to Find the Number of Nuclei of Element A at Time t0?

    Homework Statement Nuclei of radioactive element A are produced at rate t^2 (where t is time) at any time t. The element A has decay constant λ. Let N be the number of nuclei of element A at any time t. At time t=t0, N is minimum. Then N at t0 is what? The Attempt at a Solution N(t) = kt^2...
  12. K

    The title for this content could be What are Spherical Even Even Nuclei?

    Hello, I came across the name spherical even even nuclei in an exercise about the hyperfine structure. What does it refer to? That the number of protons and the number of neutrons are both even? So that there is no nuclear magnetic moment?
  13. H

    Charge distribution of nuclei affect the electronic charge density?

    As I mentioned, I want to know if the cahrge distribution of nuclei has any influence on electronic properties. And what can cause a change on the nuclear charge distribution!
  14. A

    Exploring the Diffused State of Electrons Around Nuclei

    An electron doesn't move in an orbit round the nucleus. It is in a diffused state. Please explain what is the meaning of this statement and what is diffused state.
  15. G

    Boosting Nuclei Spin: The Role of Angular Momentum & Circularly-Polarized Light

    I know that in order to create a high-spin nucleus, that you slam a nucleus into the target nucleus off-center so that when they fuse, it has a large angular momentum (relatively speaking). However, can't you add angular momentum to the target nucleus by instead just shining...
  16. S

    Can hypernuclei with multiple strange quarks be formed and observed?

    What are the strangest known nuclei? Specifically, have any nuclei with strangeness over 3 been seen? Are there any known charming or beautiful hypernuclei? Considering that Be-8, with half-life 10-16 s is a well described nucleus, the 10-12...10-13 s lifetime of charming and beautiful...
  17. I

    Why do nuclei like Uranium and Thorium have such long half lives?

    Why is it that those atoms, with atomic numbers of 90 and 92 have much, much longer half lives than atoms like Radon, Radium, and Polonium? I do realize that atoms with even atomic numbers are more stable than ones with odd numbers, so it makes sense why atoms like astatine, actinium, and...
  18. E

    Two reacting nuclei, maximum distance to overcome the coulomb barrier

    Basically I'm trying to find out how to find the maximum distance between two deuterium nuclei in order to overcome the coulomb barrier, causing them to fuse. Thanks
  19. H

    Elastic collision problem involving nuclei

    Homework Statement Two nuclei make a head-on elastic collision. One nucleus (mass m) is initially stationary. The other nucleus has an initial velocity (v) and a final velocity of (-v/5). What is the mass of this nucleus? Homework Equations conservation of momentum...
  20. I

    Why is iron-56 the most stable nuclei?

    This probably seems naiive, but why? My main question being that why isn't hydrogen the most stable. It is the simplest and should be, right? If everything wants to arrive at the lowest possible energy state, why do nuclei want to arrive at iron? I can understand splitting atoms (fission)...
  21. F

    Understanding Nuclei Interactions: Strength of Strong and Weak Forces on Protons

    Both the strong and weak interactions are short range forces of approximately 1 fm. Two protons are separated by this distance. Which equation should i use for these two question? i) The strength of the electrical and gravitational interactions that influence each of these protons. ii)...
  22. M

    Why do different nuclei need different neutron speed for neutron capture?

    Why do different nuclei need different neutron speed to achieve fission?? My understanding is that U-235 requires a thermal neutron in order to be likely to cause a fission reaction, however Pu-239 requires the additional energy of a fast neutron in order to cause the nucleus to undergo fission...
  23. C

    Neutron Absorption of Lead Nuclei compared to Uranium Nuclei

    I have had a question that I cannot get an answer for. I recently had an exam for energy in the nucleus which included a question about why lead nuclei would be inadequate for use as a moderator in a reactor. When I got the answer for the question, it stated that the lead nuclei reflect neutrons...
  24. C

    Find typical energy of nuclei in solar core

    Homework Statement Calculate the typical energy of nuclei in solar core. Calculate thermal energy required for a proton to overcome the Coulomb barrier and get within range of strong nuclear force (10^-15m) Homework Equations None given The Attempt at a Solution I have the core...
  25. R

    Finding Original Carbon nuclei from given sample.

    Homework Statement A small animal bone fragment found in an archaelogical site has a carbon mass of 155g. When the animal was alive, the ratio of radioactive 146C to the stable 126C was 1.31×10-12. What was the number of 146C nuclei found in the sample when the animal was alive? Homework...
  26. 1

    Why Neutrons Find Nuclei Easily on Atomic Level

    and nuclei are so small(on an atomic level!). is it that there are SO many atoms around and that thermal neutrons are still incredibly fast, that if there is a reflector surrounding(lets say we're talking about a critical mass of uranium and an uncontrolled chain reaction), that the neutron will...
  27. M

    Lowest Speed Nucleus for Acceleration: 9702 Physics Q40

    Homework Statement http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9702%20-%20Physics/9702_s07_qp_1.pdf question 40 Homework Equations The Attempt at a Solution I got D, because the heaviest should have the lowest speed. But I am wrong. dnt know why
  28. N

    Neutrons don't decay in nuclei because no available states incorrect?

    "Neutrons don't decay in nuclei because no available states" incorrect? Hello, If I understand correctly, the argument for a neutron (usually) not decaying when in a nucleus, is that the resulting proton would then have to occupy a high energy level, the lower levels already being occupied...
  29. edpell

    When two deuterium nuclei are shot at each other they have some

    When two deuterium nuclei are shot at each other they have some probability of fusing into a He nuclei. At the start we have a proton and a neutron in a potential well 1 MeV deep and another proton and neutron in another well 1 MeV deep. At the end we have two protons and two neutrons all in a...
  30. D

    Molar binding energy of uranium-235 nuclei

    Homework Statement What is the molar binding energy of uranium 235 nuclei? Givem: The mass of 1 uranium nuecli is 235.0439u Homework Equations E=Δmc^2 The Attempt at a Solution mass of nucleons: m=92P+143n=236.90814u mass of nucleus: m=234.99343u...
  31. B

    Why are some nuclei more resistant to pair production?

    I've gotten interested in this pair production stuff, and I'm wondering: Why is it that some nuclei can absorb more energy than the energy needed for pair production, while other nuclei result with the incoming energy creating pair production? Is it because heavier nuclei can distribute the...
  32. T

    What forces keeps electrons from falling into nuclei?

    Homework Statement "What force keeps the electron from falling into the nucleus of the atom?"Homework Equations The Attempt at a Solution I have three hypotheses: 1. Neutrons have a negative charge (although there is not only electron capture but also b+ decay) 2. The electrons in the...
  33. B

    Understanding Decay in Stable Nuclei: How and Why It Occurs

    Is stable nuclei decay? if no then how and why know please ans me i am waiting
  34. I

    Probability and Areas Around Atomic Nuclei

    As a layperson...(Who is trying to understand the atom in a bit more detail). In the past, I have most often seen the atoms drawn with electron clouds that have bands of varying density. I understand the density of the bands represent areas of higher probability. I have often seen models...
  35. E

    Bohr-Weisskopf effect in light nuclei

    In light nuclei an apparent hyperfine anomaly can seem to be present. This is however due to the quantummechanical zero-point motion of the nucleus. Is it possible to correct for this zero-point motion in experiment?
  36. O

    Constraining final energies of neutron in nuclei interaction

    Homework Statement A thin target of lithium is bombarded by helium nuclei of energy E0. The lithium nuclei are initially at rest in the target but are essentially unbound. When a Helium nucleus enters a lithium nucleus, a nuclear reaction can occur in which the compound necleus splits apart...
  37. C

    Mass radii of some simple nuclei

    Hi, I need recent experimental data for mass radii of the nuclei of deuterium, tritium, helium 3 and helium 4. I would be grateful if someone could help me with this problem and gave me exact quotes from articles, books, etc. scientific sources.
  38. L

    Comparing Mass Reduction from Fusion of Nuclei

    1. Rank from greatest to least the reduction of mass per nucleon that accompanies the fusion of the following pairs of nuclei: a. Two hydrogen nuclei b. Two carbon nuclei c. Two aluminum nuclei d. Two iron nuclei 2. n/a 3. I know fusion is when two elements are combined and...
  39. O

    What nuclei are stable against beta decay?

    I know odd-odd nuclei are generally unstable against beta decay as the pairing term in the semi-empirical mass formula is less than zero, and I know even-even nuclei are generally stable, but I don't get the rules you apply for even-odd or odd-even nuclei. Do you have to work out the binding...
  40. K

    Why Electrons Don't Stick to Nuclei

    why the electron does not stick to the nuclei?
  41. P

    Entropy of interaction in the nuclei

    It's hard to me to understand about the interaction between protons and neutrons by the means of entropy. And Is it possible to know about an entropy of an interaction between protons and neutrons or between quarks:biggrin:?
  42. S

    Collapsed Nuclei: Possible or Not?

    Are collapsed nuclei, like are discussed in http://prd.aps.org/abstract/PRD/v4/i6/p1601_1" still thought to be possible?
  43. L

    Tokamak using elctrons instead of hydrogen nuclei

    Q.) What would happen if a *reverse-Tokamak* was created, thus reversing the electromagnets to a negative charge and repelling electrons into each other instead of fusing hydrogen nuclei, what approximate temperature would need to be used and would it work? If so what would occur?
  44. D

    What Determines the Kinetic Energy of a Nucleus?

    How do you define (by all means) the kinetic energy of a nuclei (let's say of proton)? What are the factors, equations, and other things involved?
  45. H

    Fusing Iron Nuclei: Ignition Temperature

    I am aware that fusing two iron nuclei together is highly endothermic. But at what temperature does it begin. Does anybody have a clue? I know that fusing two hydrogen nuclei begins at 10 to 14 million Kelvins and that helium fusion begins at 100 million Kelvins. It wouldn't surprise me that...
  46. haael

    Are there nuclei of only neutrons?

    My question: do there exist particles similar to atomic nuclei, but made only of neutrons? If not, then why? I suspect that this would be beta-unstable, but it should live for some time and get observed somehow.
  47. J

    How Can We Determine Recoil Nuclei Kinetic Energy in a Nuclear Reaction?

    a nuclear reaction Q value is the difference in kinetic energy of the final particle and the initial particle. how we can determine the kinetic energy only for the recoil nuclei if the kinetic energy of other particles are not given?
  48. E

    How can I describe a distribution of decay times for an individual unstable nuclei

    We all know that for an ensemble of particles we can use the exponential decay law. However, the problem I am working on requires to look at nuclei from an atomic perspective. Wikipedia says that this is a stochastic process on the atomic level. I do not have much knowledge of stochastic...
  49. L

    Heavy & Light Nuclei: Differences Explained

    What's the difference between them?
  50. H

    Stable Nuclei present during Homogeneous Nucleation

    Homework Statement Assume for the solidification of nickel that nucleation is homogeneous, and the number of stable nuclei is 10^6 nuclei per cubic meter. Calculate the critical radius and the number of stable nuclei that exist at the following degrees of supercooling: 200 K and 300 K...
Back
Top