Structure Definition and 1000 Threads

A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as biological organisms, minerals and chemicals. Abstract structures include data structures in computer science and musical form. Types of structure include a hierarchy (a cascade of one-to-many relationships), a network featuring many-to-many links, or a lattice featuring connections between components that are neighbors in space.

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  1. A

    Advice on stabilizing a tall wooden structure (just a fun/simple project)

    The structure in question is a diving (read: jumping) platform that my father and I built. Here are some pics: All measurements/approximations were made in feet or inches, so I'll present them in that form if it's not too much of a problem: The...
  2. A

    Electronic Structure (magnetic quantum number)

    Homework Statement Describe a possible set of quantum numbers for the 44th electron in mercury. The Attempt at a Solution I can't help but feel a bit embarrassed by some of the questions I ask on this forum. Nevertheless, I am having problems with figuring out what the magnetic...
  3. J

    Structure of Romantic and Sexual relationship

    ...from a sociological survey conducted in Jefferson High school. http://researchnews.osu.edu/archive/chainspix.htm Does the big circle represent their football team? :)
  4. H

    Is This Resonance Structure Valid?

    Is this valid: http://img197.imageshack.us/i/imagecct.jpg/
  5. C

    Hydrogen Red Lines: Fine Structure Resource

    Can anyone point me to a reliable (preferably online) resource that states the two Hydrogen red lines due to fine structure?
  6. nicksauce

    Stellar structure, stellar evolution, compact stars, etc. ?

    What are the best books (upper undergraduate / beginning graduate) for stellar structure, stellar evolution, compact stars, etc. ?
  7. S

    How to find the Atomic Structure of a Constituent

    For a project/idea I'm working on, I need to find the charge density of tap water. I've read that this can be determined by simply subtracting total protons minus total electrons. I've got a list of elements that are in the water, but I'm not 100% sure how to find the exact number of electrons...
  8. J

    Structure constants of a group antisymmetric?

    First, how do you put in spaces without them being deleted when i post? How does one show that the structure constants, c^{k}_{ij} of a group are antisymmetric? The context is from page 12 of Anderson's "Principles of Relativity Physics", with the statement right at the bottom: Thanks for...
  9. J

    The meaning of the sign of the wavefunction in electronic structure

    I’m hoping someone will help me fill in some holes in my understanding of the electronic wavefunction. I understand the electronic wavefunction to be a *complex valued* function of the positions of all electrons in the system. But, most descriptions of atomic orbitals refer to the various...
  10. H

    What is the value of the fine structure constant at Planck energy?

    At low energy, the value is around 1/137.036. What is the value at the Planck energy? Is it listed somewhere? After all, the renormalization of the charge (as it is also called) is mentioned everywhere. But numbers are rare ... Hz
  11. B

    COMSOL band structure of photonic crystal waveguide

    Setup: I'm trying to make the band structure for a planar photonic crystal with finite thickness, i.e., a quasi-3D problem. I only want the x-direction band structure. So, I'm using variable floquet periodic BCs for the x-direction boundaries, and 0 degree floquet periodic BCs for the...
  12. V

    C2H4 Structure: Sigma & Pi Orbitales Determinations

    I need to determine possible sigma and pi orbitales of C2H4 molecul using theory of group representations and symetry.It is asked to take from C atom all orbitales with n=2. I think it could be D2h group of symetry,bu it doesn,t have 2dimensional ireducibile representations that a...
  13. C

    Large Scale Structure of Spacetime Study Group

    Is anyone interested in going through Hawking and Ellis' book by the title above and posting questions and insights? My interest is in singularities in higher dimensional spacetime, and whether there are other ways to achieve singularities (and their zoology) besides large enough mass. I am...
  14. E

    Bending in structure. Small vehicle frame.

    Hi I need help for this structure. It is loaded as shown - point E and G is wheels added as free bearings. I need to know the bending in Beam AD and also EF. I tried isolating beam AD and see it as an statically inderteminant beam to the second degree - but i am not sure this is the right...
  15. V

    Why is the Hyperfine Structure of Hypogen Simpler Than That of Hydrogen?

    Homework Statement Hyperfine structure is the splitting of energy levels due to the coupling of the magnetic moment of the atomic nucleus and the electron’s total angular momentum. In a hypothetical atom called “hypogen” the electron is replaced by a negatively charged pion (π-) which has...
  16. R

    Quantum Physics - Fine Structure

    Homework Statement Estimate the size of the fi ne structure of the 2p con guration in hydrogen-like sodium (i.e. sodium ions with all but the last electron removed). Why can't we use perturbation theory to calculate the e ffect of the spin-orbit interaction in hydrogen-like uranium...
  17. C

    Calculating Structure Factor for Sodium Chloride Crystal Structure

    Homework Statement Sodium chloride has a face-centred cubic structure which can be regarded as a primitive cubic structure with a basis of sodium atoms at fractional coordinatese (0,0,0) (0.5,0.5,0) (0,0.5,0.5) and (0.5,0,0.5) and chlorine atoms at (0.5,0,0) (0,0.5,0) (0,0,0.5) and...
  18. D

    Impact on fence structure - (momentum exchange)

    Hello eveybody. I am attempting to solve a complex problem in a simple manner. I am not a physicist so stick with me lol. The Problem: The problem is based around determining the maximum force of a object colliding into a fence like structure. The object weighs 8kg and is...
  19. M

    Torque of a structure in zero G (space shuttle)

    I am just brainstorming here, but I am wondering about the following: Look at this picture of the payload bay doors on the space shuttle. http://commons.wikimedia.org/wiki/File:Chandra_X-ray_Observatory_inside_the_Space_Shuttle_payload_bay.jpg Each door has a torque shaft driven by an...
  20. edguy99

    Hydrogen spectrum hyperfine structure

    A detailed picture of the Hydrogen red line shows a lot of detail: The difference in the 2 largest peaks is the fine structure, the lamb shift is clearly noted, but what are the other 2 bumps just below the lamb shift in the upper chart. I was thinking hyperfine, but I don't think that...
  21. M

    Proving That a Lorentzian Structure Cannot be Put on S^2

    It is fairly easy to prove that each manifold can be given a Riemannian structure. The argument is standard: locally you give the riemannian structure and then you use partions of unity. This proof breaks down for signed metrics. Even for a manifold requiring only two charts. For example, I've...
  22. ~christina~

    Chemistry Molecular structure and analysis method

    Homework Statement \Delta9-Tetrahydrocannabinol (THC) is the primary psychoactive constituent of marijuana. Its metabolites include 11-hydroxy- \Delta9-THC (11-OH-THC) and 11-nor-9-carboxy- \Delta9-THC (THC-COOH). 1)Write down the molecular structure of these three compounds. 2)Develop an...
  23. F

    Structure of elements of the unitary group

    Hey guys, I'm having a massive brain freeze here trying to show that for any element g in the unitary group you can always represent it as s*some diagonal matrix*s^-1. The only requirement for an element to be unitary is that its hermitian conjugate is its inverse correct? Any hints/help would...
  24. M

    Crystal structure and diffraction

    Homework Statement You wish to study a crystal's structure by diffracting thermal, non relativistic neutrons from the crystal, so you go to a nuclear reactor and set up your diffraction experiment on one of the neutron beam lines. The neutrons emerge from the reactor with a range of...
  25. U

    Structure formation/Gravitational collapse

    Homework Statement Suppose that the stars in a disk galaxy have a constant orbital speed v out to the edge of its spherical dark halo, at a distance R_{halo} from the center of the galaxy. 1. What is the average density \rho for the galaxy, including its dark halo? 2. If a bound structure...
  26. S

    Which truss structure is stronger in this jpg?

    All things considered equal, would one of these truss structures be stronger than the other? Consider all heights equal, load equal, arms dimensionally equal, etc.. Just going off the angle difference of the triangles. Oh... if there is a difference in strength, how can you calculate that? Is...
  27. S

    Where find K-points data of unit cell or laatice structure?

    I am beginning study Crystal structure. I am finding K-points of unit cell each lattice structure. I have to simulation bandgap structure of all lattice structure. Tell me please! Thanks sansab
  28. D

    How do scientists know the structure of the nucleus

    was it something that was figured out solely through atom smashers?
  29. J

    How Are Quantum Numbers Derived from the Schrödinger Equation?

    let me see if I got this one right: By solving the S E for bound system u got the quantum number n l and ml. each set of numbers corresponds to a curtain wave function and electron. One gots fine structure when adding the spin up 1/2 and down 1/2. so every electron in the atom has a set of...
  30. C

    How to draw tetrahedral ice structure?

    Is there any software that can easily draw a tetrahedral ice? I was trying to draw a H2O molecule surrounded by other 4 H2O's (forming a tetrahedral ice) by ChemDraw, which seemingly was not very friendly to me.
  31. G

    Building Boron Carbide in Materials Studio: Is It Possible?

    does anyone know the structure of boron carbide (B4C)? i need boron carbide's lattice parameter and the atom positions in the unit cell, as i want to build the structure by materials studio. does anybody know how to get it? thank you very much!
  32. I

    Can the Fine Structure Constant Be Calculated from First Principles?

    Griffiths's QM textbook says on page 236 regarding the fine structure constant calculation from first principles: "If you can solve part (b), you have the most certain Nobel Prize in history waiting for you". Just for curiosity, since I'm aware that giants like Sir Arthur Eddington tried...
  33. TheFerruccio

    Designing a Lighting System for a Structure

    I wish to mathematically represent point light sources inside a structure, and figure out how much like is scattered throughout the structure. Specifically, I have lighting values of a certain amount of lux, and I need to ensure that the structure has a minimum of (certain value) lux touching...
  34. D

    The Structure of the Cosmos: A Map Revealing the Intricacies of Our Universe

    I was watching a video about the structure of the universe and they had some neat graphics showing a map of the universe and it's relation to this dark matter. Since most of the Cosmos is really far away causing our view of it to be old also, do they take this into account and correct for this...
  35. P

    A Structure Larger than the Sloan Great Wall?

    Does anyone believe, given new measurements from the SDSS, that we will discover a galactic wall that exceeds the size of the Sloan Great Wall? Also, what is larger than the galactic filaments connecting to form the walls? Can somebody please provide the proper topology of what the...
  36. D

    Question regarding wind loading and shielding effects on a structure.

    I have come unstuck in my coursework project, and cannot find any information/equations for the effects of shielding on wind loading in a structure (This is not an ordinary structure, it is an unsymmetrical sculpture made up of circular and Universal beams). So i would firstly like to find how...
  37. D

    Finding the Right Lewis Structure: Formal Charge

    with lewis structures, if i come to 2 separate structures that both seem right, and i want to know which is right, and i check the formal charge, and get: for one diagram 0:1:-1:1:1 and for the other 0:0:0:0:2 which is better, i guess what I am trying to ask is, is it preferable to...
  38. S

    Crazy idea about atomic structure

    Is it generally assumed that there is a smallest building block of matter? Or is it assumed that there is always a smaller particle within any particle? because i was thinking in my calc 2 class the other day... If you have, say, a water bottle on a table, and you assume that there is always...
  39. E

    Fulminate Ion: Resonance Struct & Most Important Contributor

    Like the cyanate ion (NCO-), the fulminate ion (CNO-) has three resonance structures. Which is the most important contributor to the resonance hybrid? Suggest a reason fro the instability of fulminate.
  40. T

    Glacial Ice Structure: Continuous Transition or Spontaneous Reaction?

    I'm not familiar with Earth science, in particular ice formation in glaciers and I hope you can bear my rather stupid question: Is the change of a "normal" ice layer into glacial ice with frozen air bubbles a continuous transition or a spontaneous reaction? Someone told me that the air...
  41. Q

    Does an electron have an internal structure?

    Ok, I know this question is very old, and it has probably been answered by now, but if the electron does not have an internal structure (like the proton for example), how does it maintain itself as an entity? Why does it not disintegrate? I've asked this question a couple of times before ,and...
  42. A

    Structure of the atom - strong interaction and colour charge.

    I am having some difficulty understanding the concept of colour charge. I realize that protons and neutrons are made up of a different number of quarks, and this is how they have the charges +1 and zero. I then realized that different quarks have color charge and that in a hadron (protons...
  43. N

    Identifying Chemical/Pharmaceutical Structures: Tips and Tricks - tIA

    what is this structure?? Can anyone help in the identification of this chemical / pharmaceutical structure, tIA...
  44. H

    Martin Kober: The relation of a unified QFT of spinors to the structure of GR

    As suggested by Marcus, I have read the whole paper and decided to start a discussion of Kober's paper by asking a few questions. The paper certaintly presents a very interesting view. Part of it is an extension of Heisenberg's work on unified QFT, that the mass originates from self-interaction...
  45. L

    Video lectures of Structure and Intepretation of Computer Programs

    Hi, I'm looking for video lectures for the classic MIT course Structure and Interpretation of Computer Programs. While MIT OCW doesn't have any videos for this course, on the internet there seems to be at least two different sets of videos claiming to be of this course. It seems that one is...
  46. P

    Question about intrinsic structure of the electron

    why is it so difficult for physicists to probed inside the internal structure of an electron ? You would think it would be easier to probed the inside of an electrons and get electrons crashing into each other since electrons are a lot less massive than protons and electrons are easier to...
  47. D

    What is the lewis structure for IO3

    what does the lewis structure of (IO3) look like??
  48. D

    What is the best way to draw Lewis structures for transition metals?

    if i am told to draw a lewis diagram for PCl^{+}_{4} does this mean a melocule of 1P atom and 4 Cl atoms, the whole molecule with a charge of +1 or is it 1 P atom and 4 Cl^{+} ions, giving the molecule a charge of +4 what does the lewis structure look like, is it P in the middle with Cl...
  49. W

    Trying to compile a function with pointer to structure as return value with gcc

    I get an error with gcc "error: two or more data types in declaration specifiers" when trying to compile something of the form: struct tag *function (...) { ...} Apparently it won't let me create functions with return values pointers to structures. I know that it's perfectly valid code, so...
  50. J

    Diagram for the Structure of BrCl4+?

    Homework Statement Draw a diagram for the structure of BrCl4+. This should be a VSEPR diagram. Homework Equations N/A. The Attempt at a Solution Br has 7 valence electrons. Cl has 7 valence electrons. 7(5)=35, but we take away one electron because of the +1 positive charge. Now I have 34...
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