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. T

    Engineering 2nd Degree Inderteminacy for Structure Using Force Method

    Dear all I am trying to find the support reactions on the following structure: The frame member in the horizontal is 8m long and in the vertical the member is 5m. To do this I am using the force method (or unit load method or virtual work method). Firstly, I removing the redundants at the...
  2. H

    Hybridisation of SO3

    Since SO3 has an expanded octet structure, the central S should form three double bonds with O, meaning S forms 3 pi bonds in total. However, after hybridisation of S, there are less than three unpaired electrons in unhybridised p-orbitals of S. How can S form 3 pi bonds when there aren’t enough...
  3. Ranku

    I Shell structure topological defects as substitute for dark matter

    Recently a paper was published 'The binding of cosmological structures by massless topological defects' which proposes how 'massless' shells can bind galaxies in lieu of dark matter. There are a few basic technical details I am looking to clarify: 1. It is mentioned in the paper that an...
  4. K

    I Status of the X17 search with the MEG II apparatus

    Status of the X17 search with the MEG II apparatus The MEGII experiment at PSI July 2024 pdf here https://indico.cern.ch/event/1291157/contributions/5887844/attachments/2900132/5085565/MEGII_X17_ICHEP2024_AP.pdf could an experimental physicist explains the data and results ? also included...
  5. R

    Reproduce band structure Kagome Fermi-Hubbard using Python

    We need to define a high symmetry point path in the Brillouin zone, we can choose: Gamma-K-M-Gamma My attempt: import numpy as np import matplotlib.pyplot as plt # lattice vectors a1 = np.array([1, 0]) a2 = np.array([-1/2, np.sqrt(3)/2]) a3 = -(a1 + a2) a = [a1,a2,a3] #high symmetry points...
  6. Leandro Bolonini

    I How Do Quantum Fluctuations Shape Cosmic Structures?

    How do quantum fluctuations affect the formation and evolution of structures in the universe on large scales?
  7. Antozoa

    Debunking the Hypervalence Theory: The Truth About Bonds in HClO4

    In HClO4 Cl forms one single bond with an oxygen and three dative bonds with the other 3 oxygen atoms. However, according to VB theory, Cl is hybridized and forms double bonds instead of dative bonds. Then, the structural formula of the molecule never shows arrows as it would if there were...
  8. C

    I Effects of gravity on planetary core structure

    Hello everyone! I joined this forum to reach out to people much smarter than me. After searching the matter, i realize this subject has been beaten to death for a VERY long time. But, as of yet, I have not stumbled upon a definitive answer to my question. Flipping through my news feed...
  9. katsui

    I can't figure out why isomers change their structure...

    I'm new to chemistry, I'm looking at isomers, chiral topics, but I can't figure out why isomers change their structure, why chirals want to change in polarized light, why cis and trans do not remain constant but produce two different structures and which of these is the real structure, where do...
  10. RobbyQ

    I Can we now explain the Fine Structure Constant?

    In this video Dirac talks about the Fine Structure Constant 1/137. Can we now explain why this is?
  11. M

    A New paper claims there is evidence of suppression of structure growth

    A paper by Nhat-Minh Nguyen, Dragan Huterer, Yuewei Wen titled "Evidence for suppression of structure growth in the concordance cosmological model" https://arxiv.org/abs/2302.01331 The abstract says: We present evidence for a suppressed growth rate of large-scale structure during the...
  12. patric44

    Definition of angular frequency in nuclear structure

    Hi all I am a little bit confused about the definition of angular frequency in the context of nuclear rotation, some times its defined in the regular way as $$ E=\hbar \omega $$ and other time from the rigid rotor formula $$ E=\frac{\hbar^{2}}{2I} J(J+1) $$ where ##I## is the moment of inertia...
  13. rogdal

    A Empirical tight-binding sp3s* band structure of semiconductors

    I'm simulating on code the tight-binding sp3s* bandstructure of certain semiconductors, such as GaAs, AlP, InP, ZnSe, etc. with spin-orbit coupling at a temperature of T = 0 K but I'm having trouble at finding the corresponding spin-orbit splitting parameters. For example, I've found in this...
  14. L

    B What is a photon's structure composed of?

    I read that a photon is an electromagnetic field but how could that be since electromagnetic fields are based on electronic and thermodynamics.
  15. M

    Engineering Calculating the safe load of a glued structure with given shear stress

    I have tried to calculate the safe load with the equation of maximum shear stress, A = 4*6*10^-4, and the given shear stress 5MPa, but I couldn't seem to get the right answer which is 18kN.
  16. Q

    Integration of structure function F2 to calculate quark momentum

    I study particle physics with “Particles and Nuclei” / Povh et al. and “Modern particle physics” / Mark Thomson and I am currently at “Deep-Inelastic scattering”. After introducing several scattering equations, such as Rosenbluth, that all include terms for electric AND magnetic scattering, i.e...
  17. A

    I Does a set of matrices form a ring? Or what is the algebraic structure?

    Square matrices are closed under addition and their own form of multiplication, but in general do not commute. What algebraic structure then describes this, along with polynomials of matrices and allows us to amend with other operations, such as differentiation or integration defined on these...
  18. G

    Analysis of systems in equilibrium: articulated structures

    Figure: My attempt at a Solution: We calculate REACTIONS: $$\sum F_x=0\rightarrow \boxed{Bx=0}\qquad \sum F_y=0\rightarrow By+A=50$$ $$\sum M_B=0\rightarrow \boxed{A=25\, \textrm{kN}}\quad \boxed{B=25\, \textrm{kN}}$$ KNOT B: $$\alpha \rightarrow \alpha =90-40=50\, \textrm{º}$$ $$\beta...
  19. J

    Chemistry Why Does IF5 Exhibit a Square Pyramidal Shape Despite Exceeding the Octet Rule?

    I thought it was trigonal bipyramidal, with iodine forming 5 bonds with 5 fluorine atoms. Actually, iodine has another lone electron pair, making it square planar. Is there a reason why iodine has another lone pair when it has already exceeded the octet rule? And how would I predict how many...
  20. M

    B Would the Giant Arc be visible from a hypothetical exoplanet?

    I recently watched History of the Universe and they talked about the Giant Arc, a large scale structure that spans 3.3 billion light years long, exceeding the hypothetical limit of 1.2 billion. The Arc was discovered last year. https://en.wikipedia.org/wiki/The_Giant_Arc They said if the Giant...
  21. Astronuc

    I Proton electric polarizability and structure (recent measurement)

    Measured proton electromagnetic structure deviates from theoretical predictions https://www.nature.com/articles/s41586-022-05248-1Meanwhile - https://www.jlab.org/human_resources/recruiting/ELECTRON-ION COLLIDER JOB OPPORTUNITIES
  22. E

    I How does diffusion of high energy electrons shift band structure?

    When an n-type material comes in contact with a p-type material to form pn-junction, electrons with the highest energy in the conduction band will diffuse to the p-side to reach equilibrium so the entire band structure on n-side will shift down relative to p-side as described in the following...
  23. C

    I Number of lines in Band Structure

    The general idea is that, number of bands=number of lines. For instance, AlAs primitive cell (one of each atom per cell) has 13 bands; that is outer most shells have 13 distinct energy values. (Al: one 3s + three 3p, As: five 3d + one 4s + three 4p) But when I calculate Band Structure through...
  24. AotrsCommander

    Structure of the Galaxy: 6 Questions Confirmed

    Summary: I am looking to confirm a few things on the structure of the galaxy as we know it to make sure I have a credible enough understanding for a sci-fi project I'm working on. Background to question: For my sins, I make sci-fi starships and ground forces wargames models as part of my day...
  25. Conn_coord

    I Lectures on the Varying fine structure constant

    A University of Oxford and Cambridge Collaboration in 2014 produced a series of lectures "Cosmology and the constants of nature". John K Webb spoke on the topic of variations in the values of fundamental constants. Latest developments here. Who else is doing similar research?
  26. LCSphysicist

    How Does a New Lagrangian Term Affect the Fine Structure Constant?

    I am having some hard time to finding out where i should start. I remember see the strucutre constant arrising when we evaluate vertices on feynman diagrams for QED interactions... But i am too ignorant to know how to proceed..
  27. vanhees71

    I The general structure of relativistic QFTs

    In a recent thread about Bell tests etc. it has been claimed my point of view of "locality" where "non-mainstream physics". Of course, I cannot give a complete summary of the foundations in a forum posting, as demanded by @DrChinese there. The most clear treatment, particularly emphasizing the...
  28. LarryS

    I Role of Fine Structure Constant in Q.E.D.?

    Why, in a nutshell, are there two coupling constants for the EM field, the fundamental electric charge, e, and the Fine Structure Constant? If a brief answer is not possible, can you recommend good literature on this subject? Thanks in advance.
  29. S

    I Is there only one structure of the universe?

    (See illustration) Object A is moving, to the right, really fast towards object B on the x axis. At (0,0) they meet. There are two rocks next to each other ahead of the speeding object A. The two rocks are shown as world lines red and green as they would exist for each observer. Assume that...
  30. T

    I Question about Electronic Band Structure

    According to this Wikipedia entry: https://en.wikipedia.org/wiki/Electronic_band_structure the discrete energy levels of an isolated atom split into N levels in a macroscopic crystalline lattice (N being the number of atoms in the lattice) forming essentially continuous bands from the discrete...
  31. ergospherical

    Other Guidance with lab-report structure

    I am about to start writing a fairly important lab-report and have a few questions about structure. The experiment can be broken down into three “sub-experiments”, which have their own methodologies and conclusions. Each involves investigating the behaviour of a different part of the apparatus...
  32. S

    A What is the Structure of Gallium Oxide?

    I have three questions regarding the material Gallium Oxide. I was reading in several articles and they introduced its structure as it has monoclinic structure and it consists tetrahedral and octahedral structures in it. What I can't understand I can connect this structure to the chemical...
  33. W

    A Spin Structure Factor Explained: Static & Dynamic

    Hi, can somebody explain the spin structure factor (static and dynamic)? how is it related to the lattice symmetry(I m working with honeycomb)? How could I implement it easily? Thanks :)
  34. Dario56

    I How Does SEM Compute Sample Structure?

    In SEM, secondary electrons are emitted from the surface of the sample computing surface structure when they reach detector while backscattered electrons give information about structure and chemical composition of internal parts of the sample. However, what I don't understand is what does...
  35. Moara

    Static structure - find a fourth relation

    First, since A and B are articulated, the moments due to A and B are zero. Now, we may call reaction forces in A, ##V_A## and ##H_A## and in the same way, call the reactions in B as ##V_B## and ##H_B##. With that and Newton's third law, I managed to find three equations (equilibrium of...
  36. Astronuc

    NASA’s InSight Mission Reveals Internal Structure of Mars

    https://scitechdaily.com/nasas-insight-mission-reveals-the-detailed-internal-structure-of-mars/ https://www.nationalgeographic.com/science/article/nasa-insight- spacecraft -reveals-first-peek-inside-mars-center https://www.nasa.gov/feature/jpl/nasa-s-insight-reveals-the-deep-interior-of-mars...
  37. Ranku

    I Dark matter and structure formation

    Could matter have formed structures in the universe, like galaxies, without the presence of dark matter?
  38. A

    I Atomic Structure: Why Does Energy Decrease with Orbit Number?

    I have read that an electron requires certain minimum energy of threshold frequency to move an orbit However the energy needed decreases with increase in shell number The transition energy is reduced with each orbit For example The energy to shift an electron from 1st to 2nd orbit is much...
  39. C

    I Longitudinal DIS Structure functions

    DIS observables can be expressed in terms of structure functions F1, F2 and FL. There exists the relation ##F_L = F_2 - 2xF_1##. We can write $$ F_L = \sum_a x \int_x^1 \frac{dy}{y} C_{a,L}(y,Q) f_a (\frac{x}{y},Q) $$ and similarly for ##F_1## and ##F_2##: $$ F_1 = \sum_a x \int_x^1...
  40. Mohammad-gl

    MATLAB Graphene band structure Matlab code

    I have this code for 3D band structure of graphene but i can't understand why while graphene first brillouin zone is hexagonal but here a rectangle form of first brillouin zone is used?E0 = 0; % coloumb integral V = -2.7; % hopping integral [eV] acc = 1.41; % c-c bond length [Angstrom] lattice =...
  41. M

    Should I consider internal forces for this hinged structure?

    Summary:: A hinged structure applied with a load, should the structure totally been calculated in order to find the resultant force? Hello, Two situations, the first is a simple structure with a 20 N load at point C. The moment-equation is composed next to it. Second situation: A hinged...
  42. snypehype46

    Riemann curvature coefficients using Cartan structure equation

    To calculate the Riemann coefficient for a metric ##g##, one can employ the second Cartan's structure equation: $$\frac{1}{2} \Omega_{ab} (\theta^a \wedge \theta^b) = -\frac{1}{4} R_{ijkl} (dx^i \wedge dx^j)(dx^k \wedge dx^l)$$ and using the tetrad formalism to compute the coefficients of the...
  43. LuccaP4

    Solid-state Physics: Fermi surface and necks in an FCC structure

    Does anyone have some bibliography about necks in FCC structure Fermi surface? I have to solve this problem and I have no idea how to start. Thanks.
  44. PandaKitten

    Working out Plane Structure via Powder X-ray Diffraction Multiplicand

    Below is the measured values for the Debye rings I obtained. I have to multiply the ratio (which is (sin^2(theta_n))/(sin^2(theta_min))) by a multiplicand until I get an integer. However for the multiplicand and the values I measured I get 1, 3, 13, ??, 4, 8, ??. These should either correspond...
  45. D

    Exploring the Structure of the Poisson Equation

    Theorem 1: There exists at most one solution ##u\in C^2(\bar{\Omega})## of the Dirichlet boundary value problem. Proof: (1) We assume there is a second solution ##\tilde{u}## of the Dirichlet boundary value problem. We compute $$\Delta v=\Delta (u-\tilde{u})\Rightarrow -\Delta u + \Delta...
  46. lelouch_v1

    I How to work in the |F,m_F> states in hyperfine structure

    Suppose that we have two atoms with one proton one electron each, and these electrons interact with each other. The states for the electrons are the singlet(S=0) and the triplet states(S=1). My question is if i have to keep the nuclear spin of the protons parallel when i write the states, for...
  47. S

    Chemistry Drawing the structure of 1,3,5 - trimethylphenol

    The picture above is the correct answer, but I do not understand why. I thought that the OH group on the top has to be prioritized and be numbered 1. But then, the structure would have to be named 2,4,6-trimethylphenol, not 1,3,5-trimethylphenol. For example, 4-chloroaniline structure looks...
  48. S

    Chemistry Drawing resonance structure for this O-CH2 ion

    ion shown: My answer: the following is the answer of the question: I identified the major contributor correctly, but the resonance structures, but the second resonance I drew is missing in the answer sheet. Can anyone tell me why the second resonance structure is not part of the answer...
  49. S

    Chemistry Drawing resonance structure for SO42

    I was told that there are six resonance structures for SO42-, as shown below. I am wondering why this structure with single bonds is not one of the possible resonance. I understand that it is unfavorable as the formal charges are spread out over all four atoms, but shouldn't is still be a...
  50. B

    I What kx/ky Values Are Used for Graphene Band Structure Plots?

    Hello, https://www.researchgate.net/figure/Top-Graphene-nanoribbons-with-zigzag-left-and-armchair-right-edges-with-disordered_fig1_258105786 With what kx/ky values are these band structures plotted? The energy dispersion of graphene is given by this , yet I am confused to what kx/ky value...
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