Structure Definition and 1000 Threads

There is a space station of the length L and uniformly distributed mass M on the low Earth orbit. One side of it always faces the Sun. Which tension will the structure experience? My attempt of the solution: bottom of the station is L/2 meters below the stable orbit at that velocity...

Just wondering about the "structure" of a determinant... How much can a determinant tell you about the entries of a matrix? How much more if you know the size of the aforementioned matrix? How much more if you know that the matrix is symmetric?(perhaps a silly question). How much more if you...

Dont have to be mean?

Lewis structure (Related! - Please Help!) I have 2 problems, please help me!please! thank you so much! Homework Statement Can you tell me if I am correct?Thank you so much!I tried acd and ac but it's wrong! :( 1. Which of the following are true about the correct Lewis structure of the SeF2...

Many interesting proofs in GR (regarding black holes and singularities, etc.) involve topological methods. However, I don't understand how a theory embodied in Einstein's equations, which appear to me to be local rules of evolution, can ever change the topology since a patch of spacetime...

I understand that the formal structure of QFT has resisted axiomatization (so far) and that what formal structure presently exists is really a set of recipes. Can somebody outline the recipe please.

Quark physics is completely out of my depths but I was wondering if, in a nucleon, they assume certain orbitals like s,p,d,f, ... Does one quark tend toward the center? Is there a valence quark? Do any symmetries form?

http://img233.imageshack.us/img233/5816/espaotempoquntico1.th.jpg Two pictures of quantum spacetimes... The theory of quantum gravity (LQG) can perform calculations and predictions on the concrete structure of space and time at the Planck scale. Equations formulas that describe...

Homework Statement CH3CH=CHCH3 What's the cis and trans structure name for this formula? Homework Equations The Attempt at a Solution I've drew the ciis and trans structure H\ /H C = C / \ CH3 CH3 this is the cis the tran is similar to...

HI, A chemical has a name of Bis(2-ethylhexyl) 1,6-hexan-1,6-diylbiscarbamate, I wonder which structure is correct (sorry it seems like I can only paste smile strings, You can see the structures by depicting them on http://www.daylight.com/daycgi_tutorials/depict.cgi)...

Homework Statement write lewis structure for SOCl2. Homework Equations The Attempt at a Solution .. .. .. :Cl-S-Cl: .. | .. :O: .. what i did was put S in the middle with a single bond on both side for Cl, each Cl has six dot. S has two at the top. I...

Hi, Could someone tell me please what is the scientific consensus(or some interesting theories) on why do muons decay and what is the mechanism of it? My understanding of particle decay is based on for example neutron wchich decays because a quark in it flips from down to up. But leptons, if...

Hey guys I've got a question and I am not sure how to go about answering it without looking up a table of characteristics of elements! Niobium has an atomic radius of 0.1430nm and a density of 8.57g/cm^3. Determine wheather it has an FCC or BCC crystal structure? Now i think you have to...

Hi, I am searching for a structure that would take a load (150kg). The problem is that I want it not to break (Sigma=P/A) but I want it not to be stiff (K=AE/L). The only parameter I have is the area A but it is opposite in the equations (I can't really change the length and I did not...

Is there a data structure like the union-find data structure, but for intersections (and the sets needn't be disjoint)? I'm looking for a data structure that stores an indexed set of sets A_1, A_2, ..., A_n, and supports the following operations: replace the sets A_i, A_j with their...

Hello! I have noticed that most advanced textbooks on QM start the development of the subject with a long review of linear algebra. In particular, they talk about pre-Banach, Banach, pre-Hilbert, Hilbert spaces and so on. Why is it necessary to invoke such abstract spaces in order to describe...

so with buoyancy and liquid pressure i am pretty sure i know the answer but i just want to confirm (please don't laugh if it's obvious) - upwards buoyancy pressure only acts on the surface of a structure that is faced down - the bottom of the structure that supports all the mass of the...

In another thread Fredrik referenced THE RICH STRUCTURE OF MINKOWSKI SPACE at http://arxiv.org/abs/0802.4345..(The math is NOT simple!) But the introduction got me wondering... around page three is this statement: So what knowledge regarding more exact models of spacetime and the relativity...

In special relativity the clock hands velocity is represented by: V = v0*(1-v2/c2)^1/2 then: What happen with electrons angular velocity in atomic structure? It may be the same?: V = v0*(1-v2/c2)^1/2 if this could be true what happen with matter?

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...

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...

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

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

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

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

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...

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...

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...

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

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...

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...

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...

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...

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 effect of the spin-orbit interaction in hydrogen-like uranium...

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...

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...

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...

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...

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...

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...

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...

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...

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

was it something that was figured out solely through atom smashers?

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...

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.

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!

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...

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...

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...