Formation Definition and 480 Threads

Hi, what is Liquid Sprays how it is formed Do u have any PDFs or textbooks related to this

It is very common to see in the literature negative formation energies reported for point defects in solids using different simulation techniques ranging from Density Function Theory to Molecular Dynamics. The authors rarely comment on what does that mean physically. I will mention here two...

Is there any reason to expect both the star formation history and the angular diameter distance to peak at around the same value (redshift ~ 1.6)?

Hi Homework Statement I shall calculate the enthalpy of formation of gaseous hydrogen chlorid at 298,15 K with the usage of thw following data: \Delta [NH_{3}+HCL ->NH_{4}] :-50,4 kJmol^{-1} \Delta H_{form} NH_{3}:-46,2kJmol^{-1} NHCL_{4}:-315kJmol^{-1} and...

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...

So I've gotten into the Method of Frobenius and all; Solved a few questions, however the most inconvenient part would be the formulation of the general equations for the final answer. Granted, the lecturer told us to not spend so much time on that segment due to its minimal weightage, but I...

Is there any way to economically produce positrons using particle accelerators or any other method?

I am not a scientist, just an observer and an enthusiast. I have read that the moon was formed by a huge collision between the Earth and another large body. I was wondering if this had any affect on the Earths position in the solar system. Could it have moved the planet at all? With the extra...

I was watching How the Universe Works, and they mentioned that planets were formed by dust particles that came together to form rocks, and that those rocks collided with one another and became larger and larger eventually forming planets. My question is why did the asteroids in the asteroid belt...

Homework Statement Homework Equations Thin lens equation: 1/f = 1/s + 1/s' The Attempt at a Solution I tried to define image and object distances for both instances and equate them. Didn't work out :( Any help is welcome!

Are there any usable simulation in the literature on the formation of a solar system? It is possible for example that a solar system has 100 big planets?

I just finished up my first class of chemistry, and have a question on something that I just can't figure out. The delta H of formation for diatomic molecules is 0. I just don't understand why this is. If there is a reaction, and O2 is one of the products, why is there no heat released when...

Hi everyone, This is my first thread so I'll try to be as clear as possible and try to follow the rules. My job is to synthesize silver nanoparticles, characterize them (TEM, DLS, EDAX, Z-POT), and then pass then on to the toxicologists. This is my thesis work to graduate. A new thing I have...

I'm thinking about the thermodynamics of electron capture: p + e --- n + v(e) + energy (That is, proton absorbs electron to give neutron, electron neutrino and energetic photons.) This is thermodynamically disfavored given the substantial energy barrier to fusion to a neutron...

Is the combination of an positive sodium with a negative chlorine neutral ? If so, what attracts and holds together other sodiums and chlorines to make a grain of salt ?

Dear Internet- As part of an introductory Astronomy course, it is time to compile a mock research proposal, specifically to give us an idea of what real scientists do. The purpose of it is to focus on a particular not-yet-understood phenomenon of astronomy, and describe the process we would...

I'm hoping someone can explain how the formation of a chemical bond releases heat. What I imagine is that, when two atoms that are about to bond come near each other, they (or at least some of their electrons) accelerate forward under the influence of an electrostatic force. When these...

Earlier today I took a break from following the thread here on the Fukushima Nuc Plant problems (very interesting, by the way) and watched some TV, specifically a show I recorded on the formation of Stars. It reminded me of something that has been bothering me for some time - Gravity and how it...

If gas has to be cooled below, say, 100 K, in order for stars to form, what is the highest redshift for star formation? What would be the necessary equations to solve this problem??

In the first part of Brian Cox's documentary series 'Wonders of the Universe', he explains how the entropy of the universe always increases, and that we are therefore headed for a state of total 'disorder' where all is left of the universe is photons and dying black holes. But wasn't this...

Hi, I was just wondering if anyone could shed some light on how this ice spike formed? All I did was fill a 4" tall, 4" diameter plastic container with water and put it in a normal refridgerator freezer. I came back the next morning and found what you see in the photos. I likely used...

Can someone explain to me in detail formation of depletion zone and doping. I thought i understood this but it confused me when it came to this depletion zone. If u dope silicone with a substance with 3 valence electrons this forms a hole right? How does atom then behave? Does it polarize...

Homework Statement Pure oxygen was first obtained in the laboratory by the French scientist Antoine Lavoisier in the 18th century by decomposing red mercury(II) oxide, HgO, to give silver mercury liquid and gaseous oxygen: 2HgO(s) \Leftrightarrow 2Hg(l) + O2 (a) From values of \Delta f...

Most people on this forum know the basic theory of black hole formation. When a massive star runs out of fuel there is no longer enough heat pressure pushing out against the gravity pulling in and the star collapses. The density of the core and resulting remnant become so large that nothing, not...

Hello According to general theory is there any explanation of tidal wave in sea due to gravitation of moon. How moon warp space time in such a way so that tidal waves are generated in sea?

First time poster and non-cosmologist. Why can't we use telescopy (across the EM spectrum) to view the formation and development of our planet? Let me explain by laying out some assumptions (correct them if they are inaccurate). - When we use telescopes (again, I mean x-ray, radio, visual...

There are many ideas on how the universe came into being. Please put ideas on how into the replies/comments, as I would love to hear, and debate them. Thanks!

Hi guys I've been trying to make a program that simulates image formation in the eye so I simulated a spherical lens behavior in 3d coordinates and I'm facing a strange results! is it normal that the refracted rays don't intersect all at the same point I began to think it's true because of...

First of all, I know that that very large stars tend to form black holes, and smaller stars, but still massive in comparison to our sun, tend to form neutron stars. My question is, if matter is lost when a star collapses into a black hole, but can still form one, why is it that it is a star...

Homework Statement When using the equation, Q=ms∆T, is the heat always positive? Homework Equations heat of formation = q/mol (but of course the moles used in this lab is a positive number)The Attempt at a Solution I'm working on the energy of magnesium lab where magnesium ribbon contacts and...

How many routes are there to the formation of a black hole? A high-mass star can evolve off the main sequence, then end up going supernova and leaving behind a black-hole remnant. In this thread https://www.physicsforums.com/showthread.php?p=3062281 , Radrook and Jim Graber pointed out that...

I know the general accepted theory to the birth of our solar system. One or more nearby stars went supernova and the shock waves caused our gas cloud to collapse forming our solar system. However, i wanted an opinion from those with more knowledge on a hypothesis that seems to make some sense...

The wake is made because the inertia forces in the system ,right? So if i have low Reynolds number the inertia forces are negligible and the flow doesn't separate ,right? So In every low Reynolds number the flow doesn't separate (no wake) but low Reynolds number also indicate a viscous flow...

What is the reaction mechanism for 1,3-dibromopropane + 2Na ---> cyclopropane? Thanks :)

Hi, I'm scratching my head over the statement from my textbook which states when determinant is non-zero, the set of vectors blah blah is a basis for r^3. That does not make any sense to me because I know when a row of zeros in a matrix occur; the determinant is zero (through Gaussian...

Can anybody explain how this inverted icicle could have come to be formed ? This mug of water had been sitting outside for a few days, last night the temperature in Edinburgh dropped to below zero, and this morning I saw that this ice stalagmite had formed. There was no source of dripping...

We know that the interference pattern forms even when photons (or electrons etc.) are sent one at a time. The photons only land on the fringe parts of the screen and not the dark part - as if directed by some underlying information about where they are supposed to go. So far so good...

I'm very confused about how metal hydrides form. I'm looking at PCI plots and I see what's happening, but I have no idea why it is. For instance: "Molecular hydrogen is dissociated at the surface before absorption; two H atoms recombine to H2 in the desorption process." Why does this...

I've taken basic college physics and chemistry courses where I learned about entropy and thermodynamics, and I can tell you that I don't know that much :) That's my background. I understand that entropy is a description of 'randomness' and possible 'states'. When I wash my hands with soap...

I just recently came across this idea, outlined in http://arxiv.org/abs/1005.3497" ). I've looked for some discussion here, but couldn't find any, so I thought I'd start one (if I missed some previous discussion, I'd appreciate a link). The basic idea is simple: to probe transplanckian...

Hello everyone; I am a new member and have little formal hard science ed, but have read many pop science books by Sagan, Hawking, and others. In light of this fact please try to formulate answers with this in mind... NO MATH SPAMMING ALLOWED lol My question has to do with the...

Suppose that we have an ellipsoidal shell of particles, all initially at rest in some frame, which are going to collapse to form a black hole. Since the cloud has a nonvanishing mass quadrupole moment Q, and Q is varying with time, we should get gravitational radiation. First let's consider...

At certain concentrations of energy, there is the possibility of particles with mass forming. How does one measure "concentration of energy": by the wavelength? Or energy density? At what concentration will this occur, and why?

Hi. This is currently an academic question - I don't have a 'spare' motor to risk at present :) Would NOx catalytic converters become unnecessary on a 'spark' engine if only relatively cold air was made available at the intake? My thinking is that NOx formation needs high high peak temps and...

Homework Statement How much energy, in joules, is released when one mole of helium-4 nuclei is formed from its individual protons and neutrons? Homework Equations 2p + 2n ----> He-4 (p is proton n is neutron) The Attempt at a Solution Book sucks at explaining...

I'm trying to find some information about models of star formation (just out of curiosity). I only have a basic knowledge of text-book physics and calc, so it's hard to get started. In particular, I'd like to know how the theory is tested. The only prediction of Nebula theory that I can think...

Homework Statement I am trying to calculate the gas formation volume factor for a reservior, however I am stuck when trying to find the value n - number of moles for a gas to plug into the equation to find Bg, this is what I know; Bg (gas FVF)= volume of gas at reservoir conditions /...

Homework Statement Enthalpies of Formation. burning methane in oxygen can produce three different carbon-containing products: soot (very fine particles of graphite), CO2 (g), and CO2 (g). A) Write three balanced equations for the reaction of methane gas with oxygen to produce these three...

Hi, Could you please explain me how to predict the rate of formation of frost around a pipe carrying cryogenic fluid if the relative humidity is known? I am not able to make any assumptions as frost is porous. Is experimental analysis the only solution to this problem ? Can it be solved...

Hello every one I hope I'm in the right place to ask this question :) well , have you heared about Dr. Emoto's ? http://www.is-masaru-emoto-for-real.com/" my friend were in US last year , and she was joining some one who provides her by these info. when she told me , it was my 1st...