Structure Definition and 1000 Threads

Hi all, I've created a structure containing various fields of data. The data in these fields is stored in matrices and is be added to at regular intervals. I'd like the system to identify the amount of inputs the fields already contain and then extend said matrices to include this new data...

Homework Statement A small particle of mass m moves in such a way that P.E.=-1/2mk(r)^2, where k is a constant and r is the distance of the particle from the origin. Assuming Bohr's model of quantization of angular momentum and circular orbit, r is directly proportional to: (a)n2 (b)n...

Hello, I'm really confused by something. Cscl is simple cubic. But how it this possible? With the cl in the middle it looks like a bcc structure. Also howcome when you have 2 caesium its bcc and not simple cubic? its the same structure yet it changes to bcc. Is it because they are both atoms...

I know that the only dark matter models consistant with the cosmic microwave background radiation require bottom-up structure formation, but all of the relevant press releases I've read are about finding surprisingly large/mature structures in the early universe. Do the same...

Hi everyone, I have a question. Can we use XRD to tell if a material has a spinel or inverse structure? If yes, how should we identify it. If not, what are the ways to differentate spinel and inverse spinel structure. I a newbie in XRD analysis. Please kindly advise. Thanks.

Hello, everyone, can you give me the details of how to figure out the high-symmetry points of the first Brillouin zone of rhombohedral structure, such as bismuth? Thank you.

So say you have a presentation matrix A for a module, and you diagonalise it and you get something like diag[1,5] well you can interpret that as A can be broken down as the direct sum of 1+Z/5Z. That is the trivial group of just the identity plus cyclic 5. What if your module is defined over...

In http://arxiv.org/PS_cache/astro-ph/pdf/9803/9803165v4.pdf" the authors use (second paragraph) "Spectroscopic observations of gas clouds seen in absorption against background quasars" to search for variations in alpha. Is my understanding correct that A) The quasars are background and...

Hello, Can anyone tell me how to draw the structure of nylon 5-12 or what site could help me with this? Thank you! -N

I'm curious why people develop these objects. Although I've seen some proofs of theorems using coset(or quotient space somtimes), it remains mysterious to me how people come up with these in the first palce. So what's the motivation for inventing coset or quotient space, logical and historical?

Hi everyone, I'm working on random materials which are coincidencely oxides and showing semiconductor behaviour... Some of these are metals and i suddenly realize MOS (which are practically everywhere). I know them, i know how they work and behave still i can't get to understand the effect of...

in a question i have been asked to assess a steel structure made of two IPE beams given the attached schematic my question is regarding the buckling of the IPE400, to find the coefficient "K" i have used the julian-lawrence nomogram. as far as buckling about the Z axis goes, the...

Homework Statement Let R be a ring and S be any set. Let R^S be the set of set-functions S \to R . Endow R^S with a ring structure such that if S is a singleton, then R^S is just a copy of R. The Attempt at a Solution It seems to me that the obvious (and perhaps only?) way to...

Suppose that the set of functions \{P^a:\mathcal S\rightarrow \mathcal L|\,a\in \mathcal L\} has the property that for all s_1,s_2\in\mathcal S, s_1=s_2\ \Leftrightarrow\ \forall a\in \mathcal L~~ P^a(s_1)=P^a(s_2). Suppose also that the following is true for each positive integer n: Given...

Hi all, I was wondering if there have been any recent (i.e., in the last 10'ish months) results / articles which either support or refute the claim made by Webb et al. in the article "Evidence for spatial variantion of the fine structure constant"? http://arxiv.org/abs/1008.3907 Also...

This is a fascinating article and chart for anyone interested in the ancestry of different populations. It's fascinating to see just how distinct from the rest of Europans that Basques and Sardinians are. Also interesting to see that the Portuguese have the most North-African admixture of any...

Considering only the 4 lower-right atoms (one unit cell), I'm somewhat confused as to why the coordinates for the center atom (b) is (1/3, 2/3, 1/2) with respect to (a1, a2, c). c is pretty self explanatory, but I don't quite get the other 2. I think one of my main confusions is where the...

I'm going through Maggiore's QFT text and he is doing the fine structure constant for the Hydrogen atom. While trying to get to the Schrodinger-like Hamiltonian, he comes to a point where he has a term proportional to \epsilon * p^2 where \epsilon = (E - m) which eventually is the energy...

A set is defined as a collection of 'objects'. Does there exist something that is not considered an object in mathmatics? The reason why I ask is because when I look up the definition of a ring, it says a ring is an 'algebraic structure' existing of a set and 2 binary operations. Why can't one...

Homework Statement Determine whether the indicated operations of addition and multiplication are defined (closed) on the set, and give a ring structure. If a ring is formed, state whether the ring is commutative, whether it has unity, and whether it is a field: The set of all pure...

Hi everybody, I would like to know if someone could explain to me what happens to the refraction index of gold at grazing angle (X-ray applications), and particularly the band structure explanation (if you have it!)... Indeed, I heard that the x-ray telescopes were made of parallel mirrors...

Homework Statement ICl_4^- Homework Equations n/a The Attempt at a Solution I has 7 valence, Cl has 7*4. Ideally, they would be 8 and 8*4, and so. (40-35+1)/2 = 2 bonds. //the +1 is from the negative charge of the ion There are simply not enough bonds to go around, so when...

Does axial force exist in a member of a structure where no force acts parallel to the member?

How do (e^2)/(4Pi x epsilon x Planck constant x speed of light) cancel to give one and make the fine structure constant dimensionless? thanks

Homework Statement Let be the density given by the expression p = pc(1-r/R) where R is tha radius of the star. Find the stratification for pressure and temperature. Homework Equations Equilibrium eq. dP/dr = -Gm(r)p/r2 Continuity eq. dm/dr = 4*Pi*r2p PS.: p == rho (sorry for not...

Homework Statement I was taking a practice exam, and it asked for the "acceptable lewis structure for Diazomethane" I had narrowed it down to two possible results but can't for the life of me figure out why one is more acceptable than the other. I attached a picture of the two choices...

I've been told that the structure of Cu Nitrate is that of a octrahedral and appears similar to the picture attached. also that the distance at which the two verticle orbitals are away from each other varries the intensity of the blue colour, with the further the orbitals being away from each...

Homework Statement Have to calculate the Electron-Degeneracy Pressure as a fraction of the total pressure in a white dwarf. Given Density and Temperature.Homework Equations (\frac{1}{5m_{e}}) (\frac{3h^3}{8 \pi})^{2/3} (\frac{\rho}{\mu_{e}M_{H}})^{5/3} The Attempt at a Solution I have...

i was asked to draw the Lewis structure of NO2-, and to write the formal charge of any atoms. so in the picture you can see my tried (the red number is the formal charge). now i also asked to decide what is the angle ONO. what i know is the shape of this molecule is Bent so the angle will...

Something strange happening here. I'm isolating the beams (which I'm allowed to do) and I get a different result for Dx with each different beam! Check out what happens when I section it at CE, and check out what happens when I section it at AD Homework Statement This structure is made...

Hello all, I'm still plugging away at the meaning of spin, and spin orbital coupling. I am at the stage where I am testing out various formulations of corrections to Schrodinger's equation and beginning to test my ideas against data. Right now I am looking at Hydrogen spectra because being a...

Hey, I would like to start a discussion about the use of set theory in mathematical physics. I myself have done research in categorical physics and have seen the debates on how it can be an alternate foundation for mathematics. We can discuss here a few things, but try to stick to these...

Hi, could someone tell me how the fine edge structure next the the absorbing edge in an XAS arises? from my understanding an XAS is a plot of absorption coefficient against energy of incoming xray. The absorption edge is at an energy corresponding to when the energy is just sufficient to...

Hi, I know QED is one of the most tested theories in all of science (and one of the most accurate) but I wanted to know if it disagreed at ALL with its predicted values of both http://en.wikipedia.org/wiki/Fine_structure_constant http://en.wikipedia.org/wiki/G-factor_(physics ) The thing...

tell me if i correct i tried to draw the Lewis structure of what i think is Barium peroxide in the picture you can see the formula. in red dot is the extra electron. thanks.

I'm trying to understand how structures based on conic sections work. For example, when people speak of a parabolic mirror or a parabolic orbit for a satalite, I know what they mean, but when they speak of a hyperbolic mirror or a hyperbolic orbit, what does that actually mean? Is a hyperbolic...

AdS/CFT has primarily focused on quark-gluon plasma, but I notice some people are trying to apply the idea to bound states such as baryons. How much progress has been made in this field? Is it possible for AdS/CFT to shed light on problems such as parton distribution functions and proton spin...

Hi! Is anyone familiar with generating band structures from DFT simulations? I am using graphene, and am trying to plot the electronic structure at the high symmetry points (K, M, and gamma). Grappling to understand this theory, my questions are: 1. Is the location of the high symmetry...

My QM is undergrad level and I don't keep up on recent breakthroughs. I'm curious what the status is on space structure. This article (Mecklenburg, 2011) uses the phrase "hidden substructure" http://prl.aps.org/abstract/PRL/v106/i11/e116803 is it similar to Zurek, 2001? "structure on...

Is there a defined change in the electron orbitals of atoms as they transition from one state to the next? Is there a connection between the average kinetic energy of an atom, its electronic structure and its state of matter?

Webb et al wrote article "Evidence for spatial variantion of the fine structure constant". http://arxiv.org/abs/1008.3907. As I understand there exists direction where fine structure constant is the smallest and the opposite direction, where it is the largest. Do maybe these directions have...

Hi, I sent this question to the quantum physics forum but got no answer, so I try here : I'm looking for a comprehensive explanation of the m-scheme method : a reference to a book/web site. The only place I found an explanation is ...

Hi all, Recently there was a paper out by Susskind et. al on the topological phases of eternal inflation. We know of eternal inflation to populate our multiverse but in that paper Susskind talks about different kinds of eternal inflation, if one pays close attention to those words, does that...

"The Probing of, Approximation to and Idealization of Structure" for Foundations Hey, Over the past six years I have worked with Lucien Hardy at Perimeter in Waterloo and Prakash Panangaden at McGill. This paper is the culmination of thoughts on physics gleaned from that work...

First post! Hey people! I hope this isn't a topic already posted before. I already used the search function but I couldn't find the question I was looking for :/ Anyways, I was curious as to why equations in physics are set up the way they are. Let me show you what I mean: KE = ½mv²...

Apologies in advance if this has been asked and answered somewhere else, I searched but could not find anything. I just wanted to verify if my intuitive understanding of why space time (if it is to be physically plausible) can not be compact. According to Hawking and Ellis (and others)...

I've got several thoughts, but none of them is complete. A general explanation is that when a few atoms form a structure with lowest energy, then when the interfacial energy is low, these independent small groups of particles tend to gather together and form periodic structure. But why are...

The question might be a little stupid but I think that since I am very new to the biological world, I must ask So, I am a biomedical engineering student with probably very little biology background as I entirely change my filed. I have biochemistry as one of my courses and the problem is...

Hello, I have to make a support structure for a chimney. When I make the structure I need to know if it will fail or will stay up. Does anyone kno how I will be able to calculate this? It will be a structure with four corners and cross bracing across them. Thanks. Rob

Taking an example as: [CuCl4]2- (charge =-2) I finding it very confusing to decide whether the structure would be dsp2 or sp3? There will 9 electrons in d orbital of Cu2+ in this compound. In the presence of Cl- ligand will one electron get transferred to 4p orbital or will it stay in the...