Structure Definition and 1000 Threads

Hello, I don’t know much about physics and I am building a rack for my pickup truck. For my own safety, I need to know in how much load I can put on this rack. I drew up a diagram to clear up miscommunication for whoever wants to solve that problem. It would be highly appreciated. Distance...

In a recent online lecture it was said there is now known releationship between the masses of quarks. My online search seemed to back this up. My comparison suggests: Mcharm ≈ Mtop * fine Mup ≈ Mcharm * fine / 4 Mstrange ≈ Mbottom * fine * 3 Mdown ≈ Mstrange * fine * 7 (corrected for...

I have done the computations of band structure of cobalt adsorbed graphene. In 3x3 supercell of cobalt adsorbed (one cobalt atom) graphne, there is opening of band that is gap between conduction and valence band but there is no gap in 4x4 supercell of cobalt adsorbed graphene. I've done this in...

I know I can define a sequence on a set ##X## as a function ##a:T\rightarrow{}X##, where ##T## is a countable totally ordered set. But what about series? Can I define a series as a function ##\omega{}:a\rightarrow{}A##, where ##A\in{}X##? Or is this too general to be a series? Do I need to...

Hello, Can anybody please explain me how magnetic monopoles, fine structure constant and string theory are related to each other? Thanks

I just start to read Mathematical Methods of Classical Mechanics by Arnold. And I am sort of very puzzled by all the notion. Firstly, if the universe is seen as a 4D affine space, why is time a mapping from R^4→R? I mean this kind of 4D contains time, right? Secondly, I thought the kernel of...

Hey all, As the title suggests, I've found some recurring structure on an SEM image and I can't for the life of me figure out what it is. I took the image this morning. Here she is: http://i.imgur.com/nFuBsW2.png Here's a larger, more zoomed out and higher res version. A few more of...

Hello, I am preparing for the exam for my Matlab class, and have run into some confusion with Structure arrays. I have a hard time keeping all the concepts straight in my head. I am working on an old exam problem, where this is the structure array, which I will use as an example to demonstrate...

Although I am a newer publishing thread here, I notice this forums for a long time. And I hope someone could help me. I am doing some nuclear reaction research and want to shift myself to the nuclear structure area. I can find some references for some special topic. While I think I...

Hi all, I'm trying to compute the effect that a magnetic field has on the singlet and triplet states of positronium. I know that the positron has a charge and magnetic moment opposite that of the electron, so I'm tempted to write the interaction as: \vec{B} \cdot (\vec{M}_{1}+\vec{M}_{2})=...

In regards to the Lotus Elan from 1962, my book H-point says that Colin Chapman used the prop shaft tunnel as ''backbone'' to the body structure. Can someone please elaborate on this? Does this mean that the structure of the prop shaft tunnel acted like a stiffener for the entire body...

I am trying to figure out a method for using optical tweezers to manipulate individual atoms into new meta-material structures. I understand this would require a very complicated process. I thought of some general steps this process might use. This is roughly what I think it might require...

How to determine the bond angle based on the formula of molecules?

I am interested in knowing whether what changes would happen at the molecular and atomic level, to a material subjected to Cooling. 1. Does the minimum temperature that can be achieved has limit? 2. Is it Zero Kelvin? 3. If so, is it a global standard for minimum temperature for any material...

Hi! everyone... I'm a building a standing frame for disabled children, the structure in elemental form is shown in picture. https://drive.google.com/file/d/0B60ALttRvwKmdzRGc0pGWlN5Z3c/edit?usp=sharing link to picture -...

dear sir, i want to know the structure of the galaxies. the process that caused it happen.and finally some peculiar and intersting about galaxy.

I'm building a 6'x12' steel platform that will be 3' elevated from the ground. How can I determine what load bearing weight will be if I use 2" Square Tubing, 1/4" wall thickness and then use 1/4" angle iron for the platform structure? I was going to use 2" Sq tube, 3/8" thick, but most local...

Hey PF! I was wondering if any of you were familiar with structure functions and how they relate to turbulence? Do you know of any good articles to research? Structure functions may be defined as $$S_{ij}(\vec{R}) = \mathbb{E} \Big[ \big( u_i(\vec{x}+\vec{R}) - u_i(\vec{x}) \big) \big(...

I saw this antenna on a residential rooftop yesterday (in the US). I'm guessing it is a over-the-air Digital TV antenna, but I don't recognize the vertical bow tie structure. The antenna is about half a meter tall. Any ideas?

Hi, I'm looking for a simple s.s crystal unit cell structure and can't find it anywhere. I understand that stainless steel is a very general word and takes many forms and has many different types, but isn't there a standard type that people use in the industry and ususlay talk about when they...

dear sir, I am curious to know the way protons and neutron are arranged in the nucleus and movement of protons and neutrons in the nucleus.please guide me.

Hello again pf! i was wondering if any of you could help me with the intuition for the following structure function: $$S_{xy}(R) = \overline{\big[v_x (x + R) - v_x(x)\big] \big[v_y(x+R) - v_y(x) \big]}$$ where ##v_i## is the velocity in the ##i## direction, ##x## is distance, and ##R## is a...

I was looking at this problem. It says I should write appropriate resonance structures. But, even with resonance, I do not see how a carbon cannot fill its octet. Why does the carbon in the middle have a positive charge. Is that not unstable?

Hello, I am reading about the Western blot technique, and I am looking for clarification of the transfer step described in the wikipedia article and in this video walkthrough. It is not clear to me why the proteins should keep their shape needed for the probing step rather than breaking or...

I'm looking to prove the Global Frobenius theorem, however in order to do so I need to prove the following lemma: If ##D## is an involutive distribution and and ##\left\{N_\alpha\right\}## is collection of integral manifolds of ##D## with a point in common, then ##N = \cup_\alpha...

What do you think is the best way to structure a maths course in general? Be it algebra, calculus, analysis, probability, geometry, etc. What I mean by structure is number of exams, their percentages, type of exams, and timing of exams. I am looking for a structure that best helps students...

How much of a threat is this assembly/structure of quasars (400 billion light years long) to the homogeneity hypothesis of the universe? Is it being taken seriously in academis circles or are researchers shrugging it off for the moment? IH

Homework Statement Estimate the magnitude of the fine structure splitting in H-α in THzHomework Equations Rydberg -- R_y \left(\frac{1}{n_f^2}-\frac{1}{n_i^2}\right) = \Delta E The Attempt at a Solution This isn't really a request for solution help, and more a justification. I know that if...

Hi, I drew the lewis structure of SO2. The one with 0 formal charges gives me two double bonds. But, I see on the web that one single bond and another double bond is an acceptable resonance structure. What do they mean? Sulfur can expand its octet. Having 0 formal charge is much more...

Homework Statement Three photons coming from excited atomic hydrogen sample are picked up. Their energies are 12.1 eV, 10.2 eV and 1.9 eV. These photons must come from? A)two or three atoms B)single atom C)three atoms D)two atoms The Attempt at a Solution By solving it i got single...

I am very mixed-up with the terms perturbation, anisotropy and ripple. What is the relation or difference between them?

I'm an apprentice electrician taking night courses. My question isn't a specific mathematical problem. It's a query about a concept. Please let me know if there's a better way/place I can ask it. My text say that atoms can have a max of 32 electrons per shell, with 1-3 being ideal for...

Can anyone recommend some usufull links,pdf,... for information on large scale structure? I want to fully understand how in the cold dark matter model the the hierarchical formation of matter occurs and the role of the initial perturbations in the evolution of the universe. Thank you.

Does anyone have a Matlab file for solving the stellar structure equations that they wouldn't mind passing along? I'm trying to settle an argument with a friend that they can't really be used to describe nuetron stars and I don't have much programming experience. Thanks, Alex

In general, what's a good way to understand the structure of the universe? I'm especially curious about the nature of the edge of the universe. Relativistic concepts dealing with the expanding universe confuse me greatly. Thanks for your time!

Homework Statement Determine the force in members BF, BG, and AB, and state if the members are in tension or compression. Homework Equations Method of sections The Attempt at a Solution Now I cut the sections FB, BG and BA... I took the lower end. I now have three unknowns. I...

Hi people. I just read this somewhere and I can't get my head around it. How is the Uncertainty Relation uncompatible with the idea of a proton-electron nucleus? And can you explain why this model predicted those values for the nuclear spin? Thank you.

See attachment for question and diagrams. This problem is concerned with using the stiffness matrix method to find displacements and force in a structure. My problem is pre-eliminating the members. i have attached 2 diagrams. i would like help in trying to get from the first diagram, to the...

Hello Everyone, This is my first post. Background: I am an audio guy and seek to understand how cables contribute to the sound of my stereo. Issue: Do audio cables such as power cords, interconnects, and speaker cables "break in" as they are used? Typically, with high-end cables, users...

Recently I am reading the papers in the field of PT symmetry systems. What I am confused is that in these papers, authors directly write out the equations describe the dynamics of the given systems( For example, in this paper http://arxiv.org/ftp/arxiv/papers/1103/1103.3389.pdf , authors put...

As you can see, octet rule isn't satisfied for the central atom Xe, it has 2 more electrons attached to it. So does it mean, that you should first try to make sure octet rule works for any "side" atoms, and then you just put any remaining electrons to a central atom? (or central atoms?) And if...

In flat space the atoms in a metal have regular packing structures. A slight curvature of space would mean this wasn't geometrically possible. As a consequence do we expect metals to have a significantly lower density with a slight curvature of space? Obviously, this doesn't just apply to...

Homework Statement I want to find the force in the vertical purple member. Assuming I know the forces in all the other members, there's a problem with working out the force in the purple member. (Bear in mind, I'm using the method where I assume equilibrium at each joint in the...

Homework Statement This is not homework, I am trying learn fine structure. This site is reliable : http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html, can you tell me if the content of "hydrogen fine structure" is still valid or dated?. Even if it were classical oudated model, I'd like to...

Homework Statement The atomic mass of Niquel is 58.7 amu (atomic mass unit), and it's density (at 90ºC) is 8.86 g/cm³. (a) Find the distance from one atom to the closest one from him.Homework Equations 1 amu = 1.66053*19⁻²⁷ The Attempt at a Solution I started by finding the number of atoms...

Homework Statement Consider a star of radius R, with density p that is constant, composed of classical, nonrelativistic, idealg gas of fully ionized hydrogen. a. Solve the equations of stellar structure for the pressure profile, P(r) with the boundary condition P(R)=0 b. Find the temperature...

Hi everyone, I have a square matrix J \in \mathbb{C}^{2n \times 2n} where, $J=\left(\begin{array}{cc}A&B\\\bar{B}&\bar{A}\end{array}\right)$ A \in \mathbb{C}^{n \times n} and its conjugate \bar{A} are diagonal.Assume the submatrices A,B \in \mathbb{C}^{n \times n} are constructed in a way...

Homework Statement Hi, I am having trouble with the following problem and I can't seem to find any examples: I am trying to determine reactions at points A and D of the redundant structure below using the unit load method, there is a 10kN load at the top left point (B), all lengths are...

Atoms in solid are more closedly packed as compared to liquid and gases. But we exert more force, some solid gets compressed but liquid doesn't, why? If atoms are loosely packed in liquid than solids, liquids should get compressed...

Homework Statement Draw the structure of aspartic acid at PH 4. I calculated the PI and based on that, drew the charged structure. If anyone can confirm that this is the correct structure. Homework Equations The Attempt at a Solution I attached the structure. Thanks for any assistance.