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. K

    Writing Electronic Structure Code

    Hello all, In my research, I use DFT from time to time using SIESTA or VASP. I have spent much time reading up on the various aspects of DFT and think I have a pretty good handle on it. In order to prove this to myself, I would like to start to write my own code. I am however finding that...
  2. Orion1

    Age and structure of the Universe

    A recommended lecture on the age and detailed structure of the Universe, listed in reference 1. George Smoot is a Nobel Prize in Physics laureate for his work on COBE.Primordial fluctuations simulation by Andrey Kravtsov: Reference...
  3. Amith2006

    Fine structure of spectral lines

    While going through some concepts in spectroscopy, i got stuck in fine structure lines. So, i need some clarifications in this topic. Now, it is known fact that fine structure lines can be explained by the concept of electron spin. Aren't these lines as a result of spin orbit interaction? Apart...
  4. N

    Structure of the wave function space F

    hello all
  5. W

    Any help on how to draw the structure of CCAGAT, a hexanucleotide

    any help on how to draw the structure of CCAGAT, a hexanucleotide segment of DNA??
  6. W

    Structure of the modified nucleoside 2',3'-dideoxy-3'-fluorocytidine

    how would i even begin this problem: Draw the structure of te modified nucleoside 2',3'-dideoxy-3'-fluorocytidine
  7. S

    Optical Spectroscopy and Atomic Structure

    Homework Statement Calculate the energy and radius for each of the five lowest (n = 1,2,3,4,5) electron orbits in a Helium atom with only one electron. Enter the energy as a positive value in units of "eV" and the radius in units of "nm". Hint: The Helium nucleus has 2 protons so Z = 2 and...
  8. B

    Is My Lie Algebra 4D or 5D Given These Structure Constants?

    I have five generators of a lie algebra, g_1,g_2,g_3,g_4,g_5 which at first glance I believe are independent, although I could be wrong. I have calculated the structure constants, i.e. \left[g_i,g_j\right]=f_{ij}^k g_k And from that I have calculated a matrix rep using...
  9. E

    Cup product structure of the n-torus

    I have some questions about an example in Hatcher's "Algebraic Topology". This book is freely available online at http://www.math.cornell.edu/~hatcher/AT/ATchapters.html and I have attached the relevant part. My questions are about Example 3.11 where Hatcher computes the cup product structure of...
  10. S

    Ground state energy in Optical Spectroscopy & Atomic Structure

    Homework Statement I just want to know if there is a relationship between the ground state of Hydrogen which is 13.6 eV and the ground state of Helium. The problem is asking me to find the ground state of Helium, but I am not sure how to go about it. Any advice? Homework Equations...
  11. S

    What Is the Nearest Neighbor Distance in an FCC Lattice of Aluminum?

    Hi all I am new here but i have a major question, iv been told by people that this question is easy but I am just going around in circles with it and i was wondering if you could help. here is the questionAluminium cystallises in the fcc structure with a single atom basis. the lattice constant...
  12. J

    Atomic structure and determing effective nuclear charge

    Homework Statement The 3s state of Na has an energy of -5.14 eV. Determine the effective nuclear charge. Homework Equations Zeffective = Z - S (not listed in textbook, found this online when trying to figure out the problem) The Attempt at a Solution Nothing in the textbook in...
  13. L

    Problem with caclulatin forces in structure

    Hallo all, I have been working on a little problem. I have to calculate the forces on a certain structure, but I can not seem to find the solution. I have given a picture, drawing with my attempt and the drawing of how I try to solve it. The first drawing is to find the first forces...
  14. E

    Chemistry H NMR Spectrum - Molecular Structure

    Homework Statement Give the structure of C8H8O3.Homework Equations IR tells us that there is an OH group and a C=O group Degree of saturation = 5 --> Benzene ring + C=O H NMR spectrum shows: Peak at ~7.8ppm integrating for 1H and is a doublet Peak at ~7.45ppm integrating for 1H and is a...
  15. L

    How to Calculate Structure Constants of SU(N) Using Kroenecker Deltas?

    Hi there, Does anybody know how to exploit the product of structure constants of SU(N) through Kroenecker deltas? I mean \sum_a f_{abc}f_{ade} I know this for SU(2) as in this case I have the Levi-Civita symbol but in other cases I was not able to recover it in literature. Any...
  16. A

    Atomic Structure: Impact of 663nm Photon on Excited Hydrogen Atom

    If a photon of wavelength 663nm is incident on a hydrogen atom in its fourth excited state(n=5),then A.the atom doesn't absorb the photon B.the atom absorbs the photon but is not ionized C.the atom absorbs the photon and is ionized,with the electron having zero kinetic energy after ionization...
  17. M

    Chemistry What are the molecular geometry structures for SeO3, SeO2, and SCl2?

    Homework Statement What are the molecular geometry structure? 1. SeO3 2. SeO2 3. SCl2 The choices are: a.linear b. square planar c. tetrahedral d. trigonal planar e. trigonal pyramidal f. V-shaped
  18. wolram

    Hydrodynamics of structure formation

    [9] arXiv:0809.2330 [pdf, other] Title: Hydrodynamics of structure formation in the early Universe Authors: C. H. Gibson (UCSD), T. M. Nieuwenhuizen (University of Amsterdam), R. E Schild (Harvard) Comments: 6 pages 4 figures. Additional information at this http URL Subjects...
  19. marcus

    Upper BH mass limit, another structure formation clue?

    This paper makes the case for an upper mass limit of about 10 billion solar, for black holes. Their central black holes may help galaxies to form and may be important to understanding structure formation---an outstanding problem in cosmology. The mass limit is proposed tentatively and requires...
  20. Y

    Ideas about dark matter and structure

    Could you be more specific? You suggest that there are methods by which dark matter can dispose of kinetic energy, but can you show a method that is purely a gravitational interaction? If dark matter particles ineract with each other non gravitationally then do you agree that the dark matter...
  21. marcus

    More clues about structure formation (e.g. minimum galaxy mass)

    Structure formation is arguably the central problem in cosmology. How did the dilute gas manage to coagulate. On what timetable did stars and galaxies form? What explains the distribution of galaxy sizes and composition--clustering--the wispy cobwebby structure with its various size voids...
  22. V

    Possible Error in Chloric Acid's Lewis Structure

    Hello everyone: I was looking at Wikipedia's page on chloric acid (http://en.wikipedia.org/wiki/Chloric_acid) and was wondering if the Lewis diagram there is correct. I will not link directly to it as it has a high resolution. It shows Cl with a lone pair of electrons having double bonds with...
  23. S

    Calculating High-Symmetry Point Coordinates in Band Structure Computations

    Hi, In all the tutorials of DFT softwares I have encountered computing of the band structure for different systems by using e.g. L-Gamma-X-(U)Gamma circuits. In the texts I have read I have found about X & Gamma but what are L & (U)-Gamma? I also enountered that they have separated the...
  24. C

    Structure constants of su(2) and so(3)

    SU(2) and SO(3) "have the same Lie algebra". While I understand that their corresponding lie algebras su(3) and so(2) have the same commutator relations \mbox{SO(3)}: \left[ \tau^i, \tau^j\right] = \iota \varepsilon_{ijk} \tau^k \mbox{SU(2)}: \left[ \frac{\sigma^i}{2}...
  25. R

    Pauli Matrices and Structure Constants

    Hey folks, I am trying to generate the Pauli matrices and am using the following formula taken from http://en.wikipedia.org/wiki/SU(3 ) "In the adjoint representation the generators are represented by (n^2-1)×(n^2-1) matrices whose elements are defined by the structure constants"...
  26. S

    Effect of Effective Mass on Material Band Structure

    Hallo ... I would like to know about the effect of the effective mass on the band structre of the materails..
  27. ZapperZ

    What Can ARPES Reveal About Many-Body Effects in High-Tc Cuprates?

    One of the best sources to learn about a particular subject area in a field of study is to read someone's thesis. In this thesis, in one shot, the author has covered rather well the technique of angle-resolved photoemission spectroscopy (ARPES), many-body physics, BCS superconductivity, Fermi...
  28. R

    Mathematica Does the word exist as a mathematical structure?

    Max Tegmark develop a hypothese in which physical reality is equated as being a mathematical structure, and further it is proposed that every mathematical structure itself is a reality on it's own. To look up this idea, see these threads: http://en.wikipedia.org/wiki/Ultimate_ensemble...
  29. E

    Structure of the Week: Is 5 Days Work & 2 Days Rest a Good Idea?

    What do you think of the (almost ubiquitous?) structure of the week: 5 consecutive days of work and then two consecutive days of rest and then repeat? I think it is pretty good for promoting healthy lifestyles.
  30. B

    MATLAB MatLab: How to add a matrix to a structure without a loop?

    Hi, I have a structure AA.BB, which goes from AA.BB(1) to AA.BB(1000). I have for example a matrix "X" of size [1000x3], which I want to add to this structure, such that it becomes like this: AA.BB(1).X(1) AA.BB(2).X(1) ... AA.BB(1000).X(1) I want the same for X(2) and X(3). Can...
  31. D

    What is the significance of the structure of numbers?

    I have an idea I'd like to share on this forum about the structure of numbers. I don't have a question as such but am interested to get some feedback on wheather my idea makes sense or if it's been addressed before, or maybe ways to extend on my thoughts. I begin by defining the nth prime...
  32. M

    Basic Structure & Behavior of The Atom Oh, and hi

    Hiya. I've gotten behind in physics lately. Disturbingly so, in fact. I just can't stand how little I know, so I've recently undertaken the task of educating myself using Wikipedia, but it's terribly hard. I may have misinterpreted some things, and some things don't make much sense at all, so...
  33. F

    Searching for Gluon Radiation Probability Equation for Z Decay Jet Structure

    Hi I am searching for the equation for the radiation probability of a gluon from a quark. I need this for an explanation of the jet structure after a Z decay. Because I heard that hard gluons are radiated with small angles to the quark. This means the energy is focused in the directions of the...
  34. M

    Algorithem & Data Structure help

    problem: Show how to find the t-th largest element (t - 1 elements are larger and n - t elements are smaller) in the set of n elements in (n - t) + (t - 1)log (n - t + 2) comparisons. I've tried as hard as I can to solve this, and I came to relalize that i need to divide the array...
  35. M

    Help with Algorithem & data structure please

    Show how to find the t-th largest element (t - 1 elements are larger and n - t elements are smaller) in the set of n elements in (n - t) + (t - 1)log (n - t + 2) comparisons. I'v etried as hard as I can to solve this, and I came to relalize that i need to divide the array into two groups...
  36. N

    Structure of an Atom: Quantum Physics & Basic Measurement

    How does quantum physics describe the structure of an atom? Is it possible to take a basic measurement an atom such as the number of proton/neutrons, and calculate the rest of the dimensions/ and properties of that particular atom?
  37. R

    Unit cells (crystal structure)

    I'm trying to clarify for myself the difference between a Unit Cell, a Primitive Unit Cell and a Conventional Unit Cell. As far as I know, Primitive Unit Cells contain only one lattice point and are the smallest possible unit cell Unit Cells are the crystal's smallest building block, and...
  38. G

    Load bearing structure made of matchsticks

    Homework Statement Ok, i have a small (optional) project, to design a load bearing structure made of matchsticks. The structure must be able to withstand the load a computer monitor (i have a 17" one). Homework Equations Now, the problem i am facing is how would the force (of gravity due to...
  39. Orion1

    Grand Unification Theory fine structure constant

    I am inquiring if anyone here is qualified to numerically demonstrate the solution to this equation? The equation is the Proton lifetime derived from the SU(5) Georgi-Glashow model listed in reference 1, eq. (19). SU(5) Proton lifetime: \tau_p \geq \frac{1}{\alpha_{(5)}^2} \frac{M_X^4}{m_p^5}...
  40. R

    Discover the Most Stable Structure and Learn Why It Stands Strong

    Most stable structure ?? Hi Could anyone tell me which/what is the most stable structure? And Why?? Thanks a lot
  41. marcus

    Loeb's perspective on emergence of structure

    This is an invited review paper by a worldclass authority, so it could be useful. http://arxiv.org/abs/0804.2258 Let there be Light: the Emergence of Structure out of the Dark Ages in the Early Universe Abraham Loeb (Harvard) 32 pages, 18 figures, an invited review for the UNESCO EOLSS...
  42. D

    Milo Wolff: Spherical Standing Wave Structure of Matter

    Has anyone heard of Milo Wolff? I recently came upon www.spaceandmotion.com using StumbleUpon, and read the section of quantum theory, and the interpretation of quantum theory using spherical standing waves to describe matter seemed interesting, but I couldn't find anything on it besides that...
  43. C

    Deflection and stress in a complex structure

    Hello, I have a issue which is concerned with finding the defelction and stresses in a beam. I have attached a rough figure of the beam. Please help me by giving some suggestions. thanks chaitanya
  44. A

    Linear combinations of structure constants

    I have two Lie algebras with structure constants f^{a}_{bc} and g^{a}_{bc}, the number of generators being the same (as will become clear). Due to a particular symmetry/construct, I have that the system needs to be valid under g \to af + bg (and a similar transform for g), which leads...
  45. N

    Structure and Interpretation of Classical Mechanics

    This is an unusual book which uses the Scheme programming language to functionally describe the various components of classical mechanics. I would say it is at the level of a graduate mechanics course (think Goldstein), however students with a strong programming background will find it easier...
  46. S

    Chemical structure of Acetyl-Phosphate

    Acetyl phosphate is produced during acetate fermentation. I can't find the structure for it anywhere. The precursor in this case is Acetyl-CoA, which has the the structure H3CO-S-(Coenzyme A). And of course I know the structure of a phosphate ion. So the only question really is, does...
  47. J

    Exploring the Inter-Relationship of Nature's Constants

    Hello all. I only have a few posts here so I am somewhat new to the forum. I have been reading a number of the posts though and I am favorably impressed by many of the responses. I am also somewhat new to LaTex so please forgive my mistakes with it. I am interested in learning more about the...
  48. S

    Why Is the Fine Structure Constant Still a Mystery?

    A lot of scientists say that fine structure constant is still a mystery..one of them was Richard Feynmann...i know fine structure constant is a dimensionless constant and there are many dimensionless constant but why this fine structure constant takes special place?can anyone tell me why this...
  49. M

    Few simple questions about atomic structure and properties

    Homework Statement a)what property of graphite is the result of the presence of delocalized electrons? b)what is the reason for the generally low melting point of group I A metals as compared with the high melting points of metals in the center of the transition series? The Attempt at...
  50. K

    Optimizing Material Strength: Fact or Fiction?

    Dear experts - I'm writing a novel in my spare time, and would appreciate some help with a little bit of research. Some of the story is set in the distant future, where super strong materials are available. My problem is that I don’t know how to describe these super materials. I want to...
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