What is Single particle: Definition and 40 Discussions

Single particle analysis is a group of related computerized image processing techniques used to analyze images from transmission electron microscopy (TEM). These methods were developed to improve and extend the information obtainable from TEM images of particulate samples, typically proteins or other large biological entities such as viruses. Individual images of stained or unstained particles are very noisy, and so hard to interpret. Combining several digitized images of similar particles together gives an image with stronger and more easily interpretable features. An extension of this technique uses single particle methods to build up a three-dimensional reconstruction of the particle. Using cryo-electron microscopy it has become possible to generate reconstructions with sub-nanometer resolution and near-atomic resolution first in the case of highly symmetric viruses, and now in smaller, asymmetric proteins as well.
Single particle analysis can also be performed by ICP-MS.

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  1. M

    I Single particle energy detection

    Hello! If I have a single ion traveling at a given energy (on the order of 10 keV), is there a way to read out its energy in real time with a single pass? Basically I was wondering if there is a device able to measure the current or magnetic field induced by the ion passing through it (while...
  2. M

    I David Deutsch's Many Worlds Interpretation and the Double Slit Experiment

    David Deutsch is a well known proponent of the Many Worlds Interpretation. His argument seems to be that a single photon in the double slit experiment must be interfering with one from another world. It is commonly held by physicists that the the photon, as a wave going through double slits, can...
  3. Diracobama2181

    Single Particle Expectation of Energy Momentum Tensor

    $$\hat{T}_{\mu v}(x)=e^{i\hat{P}x}\hat{T}_{\mu v}(0)e^{-i\hat{P}x}$$, so $$\bra{\overrightarrow{P'}}\hat{T}_{\mu v}(x)\ket{\overrightarrow{P}}=e^{iP'x}\bra{\overrightarrow{P'}}\hat{T}_{\mu v}(0)\ket{\overrightarrow{P}}e^{-i\hat{P}x}$$ Now, $$\partial^{\mu}\Phi=\int\frac{d^3 k_1}{2\omega_{k_1}...
  4. DoobleD

    I How to get the wavefunction of a single particle in QFT?

    Hi folks, I'm trying to get a grasp on some of the basic concepts of QFT. Specifically, I'm trying to picture what are the actual fields of QFT and how they relate to wavefunctions. There are already many helpful posts about those concepts, here and in other places, but some points are fuzzy...
  5. L

    Derivation of FD/BE-distribution using single-particle state

    Homework Statement I'm trying to understand a derivation of the Fermi-Dirac and Bose-Einstein distributions. In my textbook Thermal Physics by D. V. Schroeder it says: "The idea is to first consider a "system" consisting of one single-particle state, rather than a particle itself. Thus the...
  6. Konte

    I Quantum thermodynamics of single particle

    Hello everybody, I have two questions: 1) Is it possible to define a temperature for single particle (or atom or molecule)? If so, how? 2) How to model with quantum Hamiltonian an exchange of energy between a single atom (or molecule) and a reservoir at given temperature ##T## ? Thank you...
  7. O

    A De Broglie Wavelength - Compound Particles, Particle Systems

    Can someone describe the physical processes which distinguish between separate and single particles when dealing with a collection of particles in the context of the De Broglie wavelength? The De Broglie wavelength is inversely proportional to the momentum of a "particle". Assume "separate"...
  8. andrex904

    Single particle state and symmetry

    Known that $$ [Q^a,p^\mu]=0 $$ where Q is a representation for the a-th generator of the algebra of group symmetry and p the 4-momentum, if we consider a single particle state, eigenstate of p $$ p^\mu | \psi_A (k) > = k^\mu | \psi_A (k) > $$ then also $$ Q^a | \psi_A (k) > $$ is...
  9. S

    Does the ubiquitousness of EM fields explain single particle

    Does the (assumption of) ubiquitousness of EM fields explain single particle interference well/better? Below is a rough logic, however it maybe need modifications. The double slit or the mach-zehnder or any object changes the configuration of time-space and EM fields. The photon may not know...
  10. jk22

    Completeness for a single particle

    Another argument than EPR that quantum mechanics were not complete by Einstein is the following : suppose a single electron passing through a hole and going further to a spherical detector. Quantum mechanics describes this as a wavefunction fulling the whole space inside the sphere and then...
  11. J

    Single particle Density Matrix meaning

    Hey guys! In an n-electron system, The second order reduced DM is defined as \Gamma (x_{1},x_{2}) = \frac{N(N-1)}{2}\int{\psi(x_{1},x_{2}...,x_{n})\psi^{*}(x_{1},x_{2}...,x_{n})}dx_{3}...dx_{n} It can be intepreted as the probability of finding two electrons at...
  12. B

    Single particle shell model for nucleus

    Homework Statement Predict the ground state spin and parity for ^{7}_{3}Li, ^{15}_{7}N. ^{31}_{15}P. Homework Equations Fill up shells for neutrons and protons separately. Shells in increasing energy are: 1S_{1/2}, 1P_{3/2}, 1P_{1/2}, 1S_{1/2}, 1D_{5/2}, 1D_{3/2} and have...
  13. H

    Relationship between single particle partition function and V

    Why when the particles are nonlocalized, the single particle partition function is directly proportional to V, namely the volume of the system, and when the particles are localized, the single particle partition function is independent of V? (Pathria, Statistical Mechanics, chapter 4, section...
  14. J

    Can the force of gravity ever be measured on a single particle?

    I haven't taken the time, but I'm pretty sure the force would be too low to ever, ever be measurable. But has anyone ever measured the force of gravity, from at least an atom? I'm not meaning the effects of gravity upon the atom, I'm meaning the exertion of gravitational force from an atom, to...
  15. F

    Spin of single particle state of free Dirac Field

    Homework Statement Show that the state d^{\dagger}_{\alpha}(0)\mid 0\rangle describes a postrion at rest by showing that it is an eigenstate of the operators P^{\mu}, Q, J^z . Homework Equations The Fourier expansion of \psi, \psi^{\dagger}: \psi = \int \frac{d^3k}{(2\pi)^3} \frac{m}{k_0}...
  16. S

    Is single particle interference explainable via entanglement?

    Do you think that: Single particle interference is explainable via entanglement? For example: in the single particle double slit experiment
  17. D

    Solution of Navier-Stokes eq for a single particle?

    Solution of Navier-Stokes eq for a single particle? Hi! I'm reading this paper on fluid dynamics: http://jcp.aip.org/resource/1/jcpsa6/v50/i11/p4831_s1 [Broken] Its equation (13) is the velocity distribution around a single bead of radius a subjecting to force fi in solution. (the subscript i...
  18. S

    Single particle single slit interference - question about the experiment

    Came across the below experiment, on Wikipedia, but don't understand how it was performed... It was shown experimentally that: in a double-slit system where only one slit was open at any time, interference was nonetheless observed provided the path difference was such that the detected...
  19. S

    Do we really need physical/real waves to explain single particle interference?

    in explaining the interference pattern that happens in double slit, single particle interference - some of the interpretations, for example De Broglie–Bohm interpretation: assumes that (some sort of) "waves" travel through both slits simultaneously and interfere with each other the...
  20. S

    Single slit single particle interference

    If we send one photon, at a time, through a single slit do we observe the interference pattern? Specially at the edges
  21. maverick280857

    Writing Down Single Particle State in P&S Notation

    Hello, In the notation adopted by Peskin and Schroeder, the single particle state is \left|\boldsymbol{p}_1, s_1\right\rangle = \sqrt{2 E_{p}} {a_{p_1}^{s_1}}^{\dagger}\left|0\right\rangle How does one write down \left\langle r|\boldsymbol{p}_1, s_1\right\rangle = \sqrt{2 E_{p}} \left\langle...
  22. W

    Why is the nuclear shell model build around single particle motion?

    Hi everyone For the past few months I have been learning about the nucleus and the nuclear shell model. The experimental evidence for a shell structure is overwhelming and easy to understand. It is also quite straight forward to obtain the correct shell closures (magic numbers) using a 3d...
  23. S

    Are the two wave functions from a double slit (in single particle int) entangled?

    http://en.wikipedia.org/wiki/Quantum_entanglement#cite_note-0" Is there an experiment where bucky balls are entangled? Many of us have heard about bucky balls showing single particle interference in a double slit experiment. However I have not heard of them being entangled. I read the...
  24. S

    Single particle Interference – Photon Vs Electron Vs Buckyball

    Is the mechanism behind the single particle interference between photon, electron and buckyball different? Reason for interference Photon - interference caused by maxwell electromagnetic waves? Electron - interference caused by Schroedinger probability waves? Buckyball - interference...
  25. Q

    What is a single particle state?

    i am studying thermodynamics statistically, and my textbook says for the perfect quantal gas, i have r single particle states, and nr occupation numbers and Er single particle energies. what do they mean? occupation numbers are the number of particles in a particular state right...
  26. Q

    Plasma physics - single particle in time-varying B-field

    It's an intro plasma physics course, and already starting to get to me... I'm asked to derive an expression for the drift velocity of a particle in a constant uniform E-field, and a slowly time-varying B-field. I've looked at a few books to see if I can even find the final result, so I...
  27. S

    The single particle density of states (Statistical physics)

    Homework Statement I'm having a little bit of trouble getting started with this problem. Can I get a little help? Using: (number of states in the six-dimensional region d^{3}x d^{3}3p) = (d^{3}x d^{3}p)/h^{3} Which provides a convenient route to the single-particle density of masses. a)...
  28. V

    Wavefunction of a single particle

    If I fire a stream of electrons at a CRT screen, the electrons go pretty much where I point them (this is how CRT Tv's work). But from reading popular science books I am led to believe that until the electron hits the screen, it has a range of possible positions and can in theory appear in any...
  29. N

    Is an atom's nucleus a single particle?

    Is an atom's nucleus a single particle? Take for example the nucleus of a lithium atom which contains three protons and three neutrons. Do the wavefunctions of these three protons and three neutrons merge together to form a single particle, in the case of the lithium's nucleus, a...
  30. J

    Can a single particle be in equilibrium ?

    Can a single particle be in "equilibrium"? If a single particle is in a double potential well (with different depths), is it correct to say it is in "equilibrium" in the statistical mechanics sense of the word? The particle will bounce back and forth and be in each well with some probability...
  31. P

    Single Particle Dynamics in EM Fields.

    Hello, I am having trouble seeing how to derive the energy equation for a charged particle from the equation of motion. The equation of motion is m\frac{d\bar{v}}{dt}=q(\bar{E}+\bar{v} \times \bar{B}) Then in the notes I have it says "projecting the eq. of motion onto the particles...
  32. Y

    Potential Energy of a single particle

    Homework Statement A single conservative force acting on a particle varies as Fvec = (-Ax + Bx5)i-hat N, where A and B are constants and x is in meters. Accurately round coefficients to three significant figures. (a) Calculate the potential energy function U(x) associated with this force...
  33. M

    Newtonian Mechanics - single particle

    Homework Statement The speed of a particle of mass [m] varies with the distance[x] as v(x)=ax^(-n). Assume v(x=0)=0 at t=0. a)Find the force F(x) responsible b)Determine x(t) c)Determine F(t) Homework Equations The Attempt at a Solution My solution to part a is F(x)=-ma^2nx^(-2n-1)...
  34. S

    Single particle interference

    Believe it or not I'm having trouble understanding quantum physics. If we take the double slit experiment and one photon is sent through the slits at a time an interference pattern is formed. From what I've read the particle goes through both slits and interferes with itself. Now when it says...
  35. U

    Hamiltonian for a single particle

    I need to find the Hamiltonian for a single particle under the influence of potential U in different coordinates: I have found the Hamiltonian for Cartesian coordinates fairly easily and would just like a check if it is: L=\frac{1}{2} m \dot{q}^2 -U with p=m \dot{q} which means...
  36. B

    Understanding Single Particle States in Quantum Mechanics

    Hi, I was just reading up on some QM, and I was wondering this: under what circumstances can you treat a bunch of electrons as occupying "single particle states", and when do you have to use one wavefunction depending on all the coordinates, psi(r1, r2, r3, ...)? Hope you know what I mean...
  37. P

    Dynamics of a single particle

    http://www.maths.uq.edu.au/courses/PHYS2100/Lnotes.pdf [Broken] Apparently it covers: Dynamics of a single particle • Vector calculus • Newton’s 2nd law • Work and line integrals, arclength • Conservative systems and conservation of energy • Central forces and conservation of angular...
  38. G

    Direction of a single particle wave

    Amateur level. Popular Science books usually start describing the double-slit experiment in terms of waves, by showing a drawing in which waves are pictured as concentrical circles emerging from the source. When passing through the slits, new concentrical circles are drawn emerging from each...
  39. A

    Find the pressure p_1 due to a single particle

    Please help. Find the pressure p_1 due to a single particle. Express the pressure due to a single particle in terms of k_B, T, L_x, L_y, L_z, and any other given quantities. I tried using pV=N(k_b)T, but it is wrong. Thank you.