What is Structures: Definition and 350 Discussions

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. happyg1

    Proving Homomorphism of F^(n) onto F^(m) with Kernel Isomorphic to F^(n-m)

    Homework Statement HI, I'm working on this: If n>m, prove that there is a homomorphism of F^(n) onto F^(m) with a kernel W which is isomorphic to F^(n-m). Homework Equations Def: If U and V are vector spaces over F (a field) then the mapping T of U onto V is said to be a homomorphism...
  2. F

    Lewis Structures for C2H3Cl: Understanding Valence Electron Distribution

    Homework Statement We need to draw the Lewis structure for certain compounds, such as C2H3Cl. Homework Equations None. I know how to draw Lewis structures, but I have a question: How do we know how to distribute the available valence electrons? For example, in drawing C2H3Cl, the right...
  3. H

    Chemistry Lewis Structures: Shapes and Hybridization & Molecular Orbital Diagram

    I don't think the problems I'm going to post are very difficult, but I'm totally clueless regarding chemistry, so they're pretty difficult for me ^^;; I also have a lot of questions to ask, so I hope you don't mind my sticking them all into one topic. I'm looking forward to your help. You don't...
  4. S

    Chemistry - energy and photons, Lewis structures

    I'm doing a practice exam that I have answers to, but I'm not sure how to go about getting to the right answer for some. Homework Statement A nitrogen laser produces pulses of light of wavelength 337.1 nm. If each pulse contains 10.0 mJ of energy, how many photons are contained in one...
  5. H

    Struggling with Math Structures Homework: Can Someone Help?

    I'm a math structures class at my college and even though i think the class is pointless its required for my degree and i have to take it. There is a problem in my book that I don't understand how to answer. The problem is: Determine each of the following without actually performing the...
  6. C

    Card Game for my Discrete Structures class

    So my teacher is making us write a paper on various games he proposed to us. This is the one I choose. You get 5 random cards from a standard deck. You place 4 of them in any order you like face up, and the last one face down. Knowing your strategy of placing the first four cards, someone...
  7. L

    What Exactly Are Resonance Structures in Chemistry?

    Hi, I'm confused by resonance structures of molecules, what are they really? My teacher said resonance structures are in fact a decomposition of the actual molecular wave-function as a sum of simpler ones. Is this true? Or are they in fact simply pictures we draw when we can not classify the...
  8. J

    Pauli's exclusion principle and fine structures

    Can anybody help me understand how pauli's exclusion principle helps explain the existence of fine line structures in the emmission spectra for atoms, which could not be explained by Bohr's model.
  9. F

    Modal Analysis for CE Structures

    Not too long ago, there was a thread in the General Physics section (I think) where someone was asking about how large buildings are evaluated from a modal analysis perspective. It was my experience that large structures had a completely analytical approach with some scale modeling. This...
  10. wolram

    The Lasting Power of Man-Made Structures

    What man made structure (large scale) can endure the longest time, i am not thinking pyramid more an/or more oom longer.
  11. Loren Booda

    Hyperbolic structures in the universe

    Most structures we see in the universe are of a spherical or circular nature. However, our universe is most likely hyperbolic (saddle-shaped) overall. Is it possible that there exist material structures on the large scale that manifest hyberbolic geometry?
  12. T

    Trouble with picturing the 3-d structures

    I know I am overthinking, as always, but for some reason I am just having so much trouble with picturing the 3-d structures (dash/wedge) when solving the problems. My test is tomorrow and I am stuck, I just can't draw them correctly...I get the hybridization, and the angle that will form. What...
  13. J

    Java I about data structures (trees) in java

    I'm trying to create this program that allows the user to create and manipulate trees. For example, a user might create a new tree with a node containing "words" as its data, then create nodes containing "nouns", "verbs", "adjectives", etc. as their data. The problem is I don't know how to...
  14. P

    Where can I find structures of oligosaccharides and homo/heteropolysaccharides?

    I'm looking for structures of ogliosaccarides and homo/heteropolysaccharides but I seem to not be able to come across any. I did searches and checked texts but unfortunately they weren't very helpful. So, can anyone tell me where I find such structures, possibly online? Thanks.
  15. Pengwuino

    The Cost of Mega Structures: Are They Really Worth It?

    http://img222.imageshack.us/my.php?loc=img222&image=86zg.jpg Now... that monster also known as the first mobile skyscraper.. costs a small fortune... or well, a large fortune... very large... $100,000,000. Now I must ask with things like these... why are they built? Now I could hear things...
  16. W

    Why Does Crystallinity Affect Strength?

    Hi, I found out that Kevlar is a crystalline structured polymer, and this is one of the factors about why its so strong. Could someone explain to me why crystallinity affects strenght? Thanks.
  17. J

    Draw the Lewis structures for the reactants and products

    I have 2 homework problems.. 1. Draw the Lewis structures for the reactants and products in the neutralization reaction between NH4Cl and NaOH. You may omit spectator ions. According to a Precipitation diagram in my book, it shows that all the elements are spectator ions, or is this...
  18. P

    Solving Strange Structures: Platt Truss Issues

    OK, I am having some issues with some trusses. The first one is a platt truss, h = 8 m, length of horizontal beams = 8 m F = 340 kN occurs at each of the 5 pts between the supports, one is a pin, the other is a roller. I get the force in a diagonal to be ~240 kN, but the answer in the...
  19. S

    CO3- (2-) Ion: Resonance Structures

    1) The CO3 (2-) ion has a maximum of a.two resonance structures involving two single bonds and one double bond. b.two resonance structures involving one single bond and two double bonds. c.three resonance structures involving one single bond and two double bonds. d.three...
  20. J

    Check Lewis Structures: Free Online Resources & Tips

    Lewis Structures... Is there any place on the web that I can check to make sure I am doing my Lewis structures correctly?
  21. A

    Calculating TM Volume Modes in Layered Magnetized Semiconductor Structures

    Hi, Did some one calculate the dispersion characteristics of TM volume modes in layered magnetized semiconductor structure?
  22. P

    Null Set: sub1 intersect sub2

    How many elements are in a sub1 intersect a sub 2 which equals a null set when a sub 1 =12 and a sub2 = 18
  23. K

    Data structures and Algorithms

    In the problems below A[1, ..., n] denotes an array consisting of arbitrary n real numbers, and A[j] denotes the element in the j-th place of the array A[1, ..., n]. 1) Let k be a fixed natural number. Consider the family A_{k} of all arrays A[1, ..., n] satisfying that for every i ≤ n there...
  24. J

    Fantastic updates on Cuba underwater structures

    "...It is true that down there at heart of the sea, are structures that sometimes have dimensions of several hundreds meters that are unusual, for which we we do not have a simple, direct explanation... " "...rocks appear. Some of them are not typical of Cuba. This leads one to think of two...
  25. J

    Question for chemists about lanthanide-carboxyl structures and their formation

    In a lab I work at at school we are trying to create aggregates of the lanthanide gadalinium along with carboxyl groups which are attached to a long (20 or so) carbon chain. The problem is we are getting polymers of lanthanides with carboxyls instead of a large number of universally sized...
  26. R

    What is the Fine Structure Constant?

    Does anybody knows a good reference or book that explains the "fine structure constant"?
  27. H

    Course on Data structures and algorithms

    Hi all,, I am just about to learn a course on Data structures and algorithms in next semester. Can u guys pls explain me the preoper importance of this course and how should i prepare myself to make full usage of this course and Lastly pls recommend some good books to me. I will be...
  28. ohwilleke

    What are Non-Spherical Structures in Astronomy?

    Most of the stuff in astronomy is spherically symmetrical, or very nearly so. Stars, galactic cores, and planets all seem to be. I can think of exceptions of such the arrangement of matter in disk like solar systems or the outer portions of spiral galaxies, small irregular asteroids, nebula...
  29. T

    What Free Libraries Can I Use to Draw Crystal Lattice Structures in 3D Using C?

    Hello, my name is Kenichi, from japan. Inorder to draw Crystal Lattice 3D Structures, what libraries for free out there to be used with C programming language ? I am still a C novice. I wonder, in chemical simulation research do you also program using C language plus some libraries to...
  30. honestrosewater

    Interpretations and structures

    A few lingering questions... Suppose an interpretation is an assignment of capital letters to declarative sentences. I see that assigning the same letter to more than one sentence limits the usefulness of your interpretation, but is it ever useful or necessary to assign more than one letter...
  31. W

    N-Type & P-Type Structures: Electron Flow

    N types have on more free electron added to its structure from doping an impurity on it. Such as an arsenic impurity onto a pure intrinsic silicon crystalline structure. However wouldn't it having one more electron inside of it that is bound to the arsenic atom make the ntype more resistant...
  32. U

    Monuments of atomic structures

    i was given this task - find at least 2 cities which have a monument of atomic structure and give the name of the element of which the structure is. :confused: for example, there's an atomic structure of iron in Brussels named Atomium http://www.trabel.com/brussel/Brussel-HeyselAtomium.htm...
  33. S

    Understand Lewis Dot Structures: Cl F & Triple Bonds

    What would the Lewis structure look like for Cl F? Would it look like this: http://img53.exs.cx/my.php?loc=img53&image=dot8pn.png How do you know when there is a triple bond? ~Thanks
  34. N

    Identify Resonance Structures

    Hey There are two questions asking me to identify the resonance structures for: SO4 two minus and H3PO4 (sorry, I don't know how to do subscripts) Could someone please explain to me how to do these resonance structures? Thanks.
  35. C

    Symmetry in crystal structures-

    Symmetry in crystal structures- please help! Hi there, I was hoping someone here could help explain a few things about crystal symmetry to me cos it hs me so confused (we've been doing crystals for 2 weeks and things up til now have been ok, I'm just getting myself muddled as usual!). The...
  36. C

    Symmetry in crystal structures-

    Symmetry in crystal structures- please help! Hi there, I was hoping someone here could help explain a few things about crystal symmetry to me cos it hs me so confused (we've been doing crystals for 2 weeks and things up til now have been ok, I'm just getting myself muddled as usual!). The...
  37. D

    Drawing Lewis Structures for VSPER: Problem Solutions

    i'm having trouble drawing up some lewis structures related to VSPER theory. i was given 22 Lewis structures to draw and i had problems with these ones... 1 - [N(CHsubscript3)subscript4]^+ 2 - IClsubscript2 3 - [IClsubscript4]^- thanks if anyone can help out with these questions.
  38. S

    Can String Theory Lead to the Ultimate Unification of Physics?

    http://www.mncs.k12.mn.us/physics/string/string_artistic2.jpg http://www.mncs.k12.mn.us/physics/string/string_index.html
  39. Math Is Hard

    C prog: printing values from array of structures

    Hello, I have a little function I have written that takes an array of structures as an argument void print_names(struct pers_info arr[]) { printf("Here is person 1: %d %s %s %s\n", arr[0].ssn, arr[0].pers_name.first,arr[0].pers_name.middle, arr[0].pers_name.last); printf("Here...
  40. maverick280857

    Easy Way to Draw Structures to Post Here anyone?

    Hi I've been wondering...there are quite a few folks who would like to post their organic chemistry problems here (including, possibly me, in future). But to do that properly, one must be able to give his/her solution/mechanism/question in the form of structures and not just words as it would...
  41. P

    DNA structures and its siblings

    I would like to ask a question about PNA and Morpholino... I am sorry, I look at their structure images but I still couldn't see anything that can be called similarities. The Morpholino has ring structure which is the same as DNA but PNA has no rings at all... Would you please explain a...
  42. Ivan Seeking

    Spiritual Interface: Right Temporal Lobe & Limbic Structures | MD Melvin Morse

    I googled for ocean, plastic, pollution, "Discovery Times", to find something that I saw last night and instead got this...what a coincidence. I assume that this is some crackpot but all considered it seemed worth a post...
  43. Loren Booda

    Forbidden structures?

    Where are uniform gravitating prolate spheriods found? Where are gravitating polyhedra found?
  44. C

    Could the Universe's Cosmic and Micro Structures be Built by One Interaction?

    I found a very interesting theory claiming that the universe is one interaction that self-reproduces self-similarly at scales of its own like a form of life. The created multiscale sources of interaction build the lumpy structures of the universe at every scale. This theory of interaction...
  45. H

    CMB anisotropies and matter structures

    CMB anisotropies are deviations of the temperature of the black body emission mainly (but not only) by photons, which have to climb out gravitational potential of higher density concentrations during recombination epoch and during their spatio-temporal trajectory till now (Sachs-Wolfe effect)...
  46. Ivan Seeking

    Deep Water Megalithic Stones and Structures Near Western Cuba?

    I have been hearing about this story for some time. I have no idea what to think. It seems to be a step above the typical fringe story so I posted here. http://www.earthfiles.com/news/news.cfm?ID=587&category=Science
  47. H

    Good Computer Program for Chemical Structures & Equations

    anyone know of any good computer programs used to make chemical structures and equations? i know of www.orgsyn.org but it's really a pain in the ass to use. EDIT: fixed the link, there was a comma in the way
  48. G

    Giant Metallic structures

    Does anyone know whether there are any relationship between the structure of a metal and its position in the periodic table? For example, I know zinc and magnesium have a hexagonal close-packing structure, but is there a reason for it? So how do you know which metal has a hexagonal...
  49. S

    News Is the Republican Power Structure Immoral and Inevitable?

    Monolithic and invincible, the Republicans have designed a truly awesome machine. Its engine is Capitalism, lubricated by Fundamentalist Christianity. Americans have not grasped yet the power of this machine, but the World has seen in Iraq the raging power that dominance in space yields. The...
  50. quantumdude

    The essence of logic is to find out what argumentative structures

    This will be the new version of my "Logic" thread in PF v2.0. I'll get my logic notes pasted into this forum ASAP, along with some of the more useful discussion from the old thread.
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