Structure Definition and 1000 Threads

Hey guys, newbie here! I stumbled upon your forum while searching for an explanation i was looking for in regards to some theories/questions i have about the shape, structure, and nature of the universe... so here goes! I have some fundamental issues/differences in opinion regarding the...

Hi, If the mass is very high and the fine structure constant very small, is it true particles of opposite charge can't annihilate? If yes. What has mass and fine structure constant got to do with annihilation?

Hi, Though this may be a basic technique, I would like to know how to make a free standing structure. Most of the papers use KOH as etchant to etch SiO2 and then get such structure. And I think besides putting SiO2 into the etchant, there should be some other things work with this...

value of fine structure constant logarithmically depend upon momentum/energy scale. so what is exact energy/momentum scale corresponds to standard/recommended value of fine structure constant?

I am trying to find the IUPAC name for this structure. I a keep coming across 1,3-diol cyclohexane, but my homework online keeps saying its wrong. Does anyone know what this structure is? Thanks:)

What is fine structure?

I understand the idea of the Lewis Structure and the octet rule. What I don't know is where to place the atoms. And unfortunately my book doesn't explain it. They just draw the lewis structur and expect us to understand how they did it. For example: Draw the lewis structure of H_2CO...

please help me name the structure. The structure is a hexane. I can't figure out how to label it. could it be: 2-methyl butane 3-bromo-4,5-ene, 5-propyl- chloro hexane?

Hello, this might be a trivial question for many of you. I would like to know what are the simplest phenomena/experiments, if any, (and perhaps the first historically) that contradict the assumption that subatomic particles like electrons, protons, neutrons..., can be thought of as "small...

I understand the physics behind the Temperature Structure Paramter, but need help find a intial value to divided by. Here what I am trying to do. dB = 10 log 10 (CT2/CT2i) What I need is an intial value (CT2i) for the temperature Structure Parameter for a monostatic sodar. The units need...

Homework Statement Can someone please try to help me with this. I have a bcc structure and the question is ''Clearly indicate the unit translation vectors and state their value in Å. I have attached the sketch : http://img440.imageshack.us/img440/4879/picture3lh.jpg are those t1,t2,t3...

Can anyone tell me how to find the reactions of this structure? If not by summing forces and moments, then how? I'm thinking it's indeterminate and assumptions have to be made.

In my engineering class, we were told to create a structure out of balsa wood (1/8"x1/8") and glue. The structure has to suport the weight of 3 15lbs. weights (donut shape). We are only give 72" of balsa wood, and the structure must hold the 3 15lbs. weights for 1min. Sorry I am new to this...

what is the moleculer structure of tooth enamel and is it similar to egg shells?

I plot the tight binding bandstructure of graphene. There is a very good aggrement with ab-inition calculation in the valence band. but there is a problem in the non-localized orbitals of conduction band especially in the Gama(0,0) point. Any suggestion is appreciated.

Hii, I was wondering whether there is any correlation between the energy eigenvalues of a single atom (say He) with the electronic band structure of a collection of He atoms. for example, for He atoms the lowest energy would be the ground state, with 2 electrons. So will the lowest band for a...

Disclaimer: I am a science buff – not a scientist. I am curious to know if there has ever been a theory developed about the infinite nature of the universe, large and small, relating to a fractal structure. I was pondering fractal subdivision, and how it offers at least the theoretical...

Assuming atoms pack together as hard spheres , find the largest intenstihal atom that can fit in a BCC arrangement of iron atoms . Take the radius of the irom atoms as 1,21 Å . Carry out the same calculations for an FCC arrangment of iron atoms . On the basis of these caluclation would you...

I have attached the problem drawing. Please refer to it. This is a lumped mass structure and all elements have the same Modulus of Elasticity and Moment of Inertia. Determine the number of degrees of freedom of the structure So I am thinking between 2 different scenarios. 1 scenario...

Hi all, long time reader first time poster! Just need a hand on this problem I've been stuck on for a few days Homework Statement Let r=(a_1,a_2...a_k) be in S_n. Suppose that ß is in S_n. Show that: ßrß^-1=(ß(a_1), ß(a_2)...ß(a_k)). Homework Equations The Attempt at a...

All I can really think to talk about is how the phospholipid bilayer (i.e. hydrophobic tails, hydrophilic heads) is structured, and how that only allows certains certain molecules in (blocks out polar molecules (except H2O), large molecules in general, ions etc.), while the others require forms...

Dear all, I have been thinking, if insulators have their valence band filled, then which band does the extra electrons go when it is negatively charged?? If it is the conduction band, then it would become a conductor... Similarly, if it is positively charged, there would be a hold in the...

Hi! I'm new here... I'm going to go right to the point. I know that when you take atoms and get them closer together, the discrete energy levels turn into bands. But when I'm facing a band structure plot, such as this one (band structure of aluminum nitride in wurtzite structure)...

If the universe is filled with matter, and that matter causes space-time to bend, wouldn't the over-all structure be closed? Meaning, if I fly off in some random direction I would eventually "wrap around" the universe like a person moving across the surface of a sphere? If so, is this...

Homework Statement [PLAIN]http://broadcastsol.com/123.JPG Prob. 1. The structure of massless members is shown in the figure. Determine the reaction forces at the supports C, and forces in the rod EF and DG. Givens: P, a, b, c. Prob. 2. The structure of massless members is shown...

Hello forum members, I got a nifty new multireference CI program at my hands and now I'm wondering what to do with it. The program is able to correlate general MCSCF wave functions, and as such basically any kind of molecular electronic structure imaginable; in particular also electronic...

Hi I was trying to understand the geometry of Sulphur Dioxide molecule on the basis of hybridisation involved in the central atom. I found that Sulphur atom should have SP2 hybridisation. I want to know that is there any promotion of electron from 3 p-orbitals to 3d-orbitals and then forming...

Is their a method for predicting the molecular shape of molecules without drawing the Lewis structure? I am preparing for an ACS exam and would like to try to save some time on these problems. I think I could determine the steric number by counting the total electrons available, and...

I just studied the structure of the lens of the eye. And I found out that there are two type of fibres present, which were the Circular Fibres and the Radial Fibres. Can anyone please tell me what is the purpose or function of these two fibres ? Or simply they are just fibres which are...

Homework Statement That's basically the whole question in the title there, ie; Derive an expression for the fermi energy of a 2d structure at 0 kelvin. 2. The attempt at a solution Basically the first part of the question had us sketching the Fermi-Dirac distribution function at 0K for...

Like, let's say substance A, in the sun, is very hot. After the sun goes down, it stays hot, but after awhile it becomes cold. Element B, in the sun, is also very hot, but after the sun goes out, it basically becomes cold immediately. Why is this?

Hi! I'm new to the physics forum but I've read a little bit and I'm impressed with the knowledge a lot of people have here. I've tried searching for any topic on my question without any luck. My question is simply what the algorithm is to determine the band structure for a one dimensional...

Hello all, I am having trouble figuring out the space group for a cubic structure having A atoms at 000 and B atoms at 1/2 1/2 0, 1/2 0 1/2 & 0 1/2 1/2. Now, I know that it is Pm3m, but what is confusing me is why is there not a 4 fold axis at the first m, thus, giving you a P(4/m)3m...

Sorry if someone already posted this link but did anyone see this in the news? http://www.nasa.gov/home/hqnews/2010/nov/HQ_10-295_FERMI.html What are people's opinions on what this might be?

What's the main reason behind the fine structure of X-Ray transition?

A crazed billionaire has a lifelong dream to build the world's tallest structure as a testament to his glory. Fearing competition, he decides that his tower must be far taller than any other in order to remain that way for as long as possible. The goal: build a 10 km tower, and do it in as...

Hi, Could someone help to explain that why for the 2 D system, like 2 dimensional electronic gas, the crystal momentum k in 2D band structure is defined on a torus? Thanks a lot.:)

"A two-dimensional structure is tested in a wind tunnel with an air density of 1 kg/m3. The wind tunnel is 1 m high, with upstream and downstream pressures of 1.5 kPa gage (i.e. above atmospheric) and 1 kPa gage respectively. If the mean velocity of the entering air is 30 m/s and the downstream...

Homework Statement Draw the skeletal structure of the compound with molecular formulaC3H4Cl4 whose proton NMR spectrum contains a down-field triplet and an up-field triplet with relative integration of 2:2. 2. Rationale for Solution Integration ratio of 2:2 means CH2-CH2, after this one carbon...

question about the universe structure? I have a question. Does universe consist curved spacetime everywhere? , I believe there are plenty of flat spacetime, isn't it? . If it is so then eveywhere worm hole is not possible isn't it?

Dear all, I want to calculate the band structure of graphene for a unit cell with 8 atoms in the Tight Binding approximation. There is no problem about drawing the band structure for a unit cell with 2 atoms. But by increasing the unit cell size, first brillouin decrease and there is a gap in...

In the book of the Dr. Ronald Askeland the problem about x-ray diffraction use the next planes indices to calculate the interplanar distance, but I don't understand why to use such planes indices? Are these planes all of planes in a cubic structure? (111) (200) (211)...

Can the density of gas be changed for good, or is the change just temporary? And what increases density in gases?

I just noticed that it's often taken for granted that a macroscopic crystal has a similar geometric structure as in the atomic scale. What is the physical explanation for this (assuming it is true)?

Hello, I'm new here and have joined to ask the following two questions: 1 - The distance to the CMB has been measured at approximately 14 billion light years. How was this achieved, what is the error and is it the same in all directions? 2 - WMAP data clearly shows that the CMB has a plane...

Hi guys, what are some ways to visualize the deflected shape of a simple structure? I know that there is no slope or deflection at fix ends. No deflection at supports (roller, fix ends, etc). Also, I am not really sure what a kink is. Thanks

Has the following explanation for the large scale structure of the universe been considered and discounted?Consider a universe many billions of times the size of the observable universe, so big that the homogeneous nature of the universe could even be an illusion. At a very large distance...

Hello... I was just reading about that, and I have one question. In the chapter I've jut read about, the overall headline is about one electron atoms, so I was just wondering, since the overall equation got Z (Atomic number) in it, if this was for larger atoms as well, or ONLY one electron...

What happens to the atoms in a spring when the spring looses its elasticity in hookes law? I am aware of the hookes law F =-kx but for my assignment i am also to state what happens to the atoms when the spring becomes plastic and deforms how and why? my asumtion is that they atoms...

Homework Statement NaCl is a face-centred cubic with a basis at Na(0,0,0) and Cl at (a/2,a/2,a/2) and lattice parameter a = 5.63 angstrom. calculate the separation between nearesr neighbours (Na and Cl). The Attempt at a Solution Just by looking at the NaCl structure the separation...