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I'm looking for contemporary reviews on neutron stars. Seems like this area is pretty active, so even reviews from five or ten years ago are somewhat lacking, though certainly not worthless. Does anyone have recommendations? Newer is better.
Books are okay too, but I'd prefer one of those 70-ish page reviews you find i... |
Ok, I've stumbled onto what I think is a bit of a paradox.
First off, say you had some computer in a very fast(near light speed) centrifuge. You provide power to this computer via a metal plate on the "wall" of the centrifuge's container, so it works similar to how subways and streetcars are powered.
If the computer n... |
How to do this?
Show that if the tension $F$ in a string is changed by a small amount $\mathrm dF$, the fractional change in frequency of a standing wave, $\frac{\mathrm df}{f}$ is given by:
$$\frac{\mathrm df}{f}~=~0.5\frac{\mathrm dF}{F}.$$
|
Okay, I'm asking a question similar to this one here: Time Dilation - what happens when you bring the observers back together?. Specifically, I am curious about a specific angle on the second part of his question, regarding when two moving frames of reference (FoR) are brought back together, and how "it" knows which on... |
How did these guys get the masses from Heim Theory?
I won't even bother to ask about validity as I read the other post on this. So I know how we all feel about that. I hadn't even heard of it till today when I stumbled across it searching for something else. But I'd like to know: How did they get the subatomic particle... |
In the past few days I've become increasingly intrigued by the QHE, mainly thanks to very interesting questions and answers that have appeared here. Unfortunately, I am as of yet very confused by all the (seemingly disparate) stuff I learned.
First, here are some random points that I've been able to gather
I(nteger)QH... |
I'm trying to amass a list of physics books with open-source licenses, like Creative Commons, GPL, etc. The books can be about a particular field in physics or about physics in general.
What are some freely available great physics books on the Internet?
edit: I'm aware that there are tons of freely available lecture n... |
How can we relate inflation and string theory? We study some inflationary cosmological model or some string cosmological model under some specific assumptions or conditions.
Is their any relation or any difference between these two concepts? My knowledge of inflation is that it is a theory or concept to resolve some s... |
That pretty much says it.
Suppose I have some powder of $NaCl$. It is kept in contact with itself in vacuum. You are free to remove all the disturbances that bother you.
Is that true that, well, there exist a ($\mbox{very}^\mbox{very}$ large) amount of time $T$ that for every moment $t>T$ you will have a single beauti... |
If I apply $1 \text{ V}$ across a $1 \text{ }\Omega$ resistance, I'd get $1 \text{ A}$ flowing. $1 \text{ A}$ is defined as $1 \frac{\text{C}}{\text{s}}$, and $1 \text{ C}$ is equivalent to $6.24150975 × 10^{18}$ electrons.
Therefore, Ohm's Law describes only the number of electrons passing a given branch per second. H... |
I am trying to solve this simple excercise:
Question
You throw a small coin upwards with $4 \frac{m}{s}$ . How much time does it need to reach the height of $0.5 m$ ? Why do we get two results?
Answer
(We get two results for time, because the coin passes the 0.5m mark downwards too.)
The equtation I used (for constant ... |
Can anyone give me a quantum mechanical explanation of the theory of valence? (i.e. why atoms bond just enough to have a complete orbital)
EDIT: To clarify, I already have an idea of why atoms bond, and the molecular orbit makes sense to me. The problem is that the valence bond theory provides a simple and fairly accur... |
In general relativity, light is subject to gravitational pull. Does light generate gravitational pull, and do two beams of light attract each other?
|
Photons are massless, but if $m = 0$ and $E=mc^2$, then $E = 0c^2 = 0$. This would say that photons have no energy, which is not true.
However, given the formula $E = ℎf$, a photon does have energy as $ℎ$ is a non-zero constant and photons with a zero frequency do not exist.
What am I missing here, or does the famous f... |
Can you build an afocal zoom system with only one stage. It looks like you would have to use more than three lenses. You would probably have to have all but one of the lenses be fixed; but it might be possible to have more than one moving, as long as they are all moving the same distances (i.e. they are on the same s... |
If I am driving a car in the rain, and want to increase the available traction, should I:
Increase pressure in the tires
Decrease pressure
Leave the pressure set to optimum dry pressure
Increase or decrease just the front or back tires
Does the answer change if the surface has no standing water (i.e. is merely wet)?
... |
I took an introductory chemistry course long ago, but the rules seemed arbitrary, and I've forgotten most of what I learned. Now that I have an undergraduate education in physics, I should be able to use physics to learn general chemistry more effectively. What resources, either books or on-line, are useful for physi... |
Suppose we have a sphere of radius $r$ and mass m and a negatively charged
test particle at distance d from its center, $d\gg r$. If the sphere is electrically neutral, the particle will fall toward the sphere because of gravity. As we deposit electrons on the surface of the sphere, the Coulomb force will overcome gr... |
I saw a paper on arXiv that referenced this approach to an ontology of QM:
Phys.Lett. A213 (1996) 1, S. Mancini, V. I. Man'ko, P.Tombesi Symplectic tomography as classical approach to quantum systems
http://arxiv.org/abs/quant-ph/9603002
An introduction to the tomographic picture of quantum mechanics
http://arxiv.or... |
Does it violate any physical laws to take a portion of the energy out of a system and use it? Specifically I'm referring to heat. (Kinetic energy).
For example, if you have a material which has a lot of energy and has a high temperature, is it possible to take a portion of that energy and use it for something else, and... |
Two towns are at the same elevation and are connected by two roads of the same length. One road is flat, the other road goes up and down some hills. Will an automobile always get the best mileage driving between the two towns on the flat road versus the hilly one, if operated by a perfect driver with knowledge of the... |
It might seem obvious but i can't imagine how is gravitational pull is different from acceleration due to gravity?
|
How do the wheels of a train have sufficient grip on a metal track? I mean both of the surfaces are smooth (and not flexible) and it is okay if there is no inclination, but how about on an inclined track?
|
The mathematical concept of function is used in physics to represent different physical quantities. For example the air pressure variation with time and space is called an acoustic wave. We use a function to represent a charge distribution (or even electric field strength) in space and time.In gravitation we use it to ... |
I sometimes hear statements like:
Quantum-mechanically, an interference pattern occurs due to quantum interference of the wavefunction of a photon. The wavefunction of a single photon only interferes with itself. Different photons (for example from different atoms) do not interfere.
First of all -- is this correct?
... |
In Nielsen and Chuang's text on Quantum Information and Computation, the measurement postulate is stated by using a collection of measurement operators and the outcomes are the indices of the measurement operators. See: http://books.google.com/books?id=65FqEKQOfP8C&lpg=PA87&ots=Pq9S_kl6GO&dq=measurement%20postulate&pg=... |
The standard textbook treatment of the conformal gauge for a free string with BRST ghosts is fine, but when a string splits into two, we have Gribov ambiguities for the conformal gauge. We can impose the conformal gauge for the initial string before the split, and also the final two strings after the split, but not for... |
In 2000, Nasa conducted an experiment and found that gravity plays an indirect role in flame formation and composition (see the wikipedia article). What role does gravity play? Why does a flame extend in the opposite direction of gravity? Assuming the experiment could be re-created, are there any other forces that w... |
I have been struggling with these Majorana fermion identities for quite sometime now. I would be grateful if someone can help me with them.
Let $\lambda$,$\theta$ and $\psi$ be $4$-component Majorana fermions. Then apparently the following are true,
$(\bar{\theta}\gamma_5 \theta)(\bar{\psi}_L\theta)(\bar{\theta}\gamm... |
I have trouble interpreting this illustration. I see why r (position) and a (acceleration) are the way they are, but what happened to v? Why is it smaller than its coordinates? Is this another error in my textbook?
|
I'll break this down to two related questions:
With a fission bomb, Uranium or Plutonium atoms are split by a high energy neutron, thus releasing energy (and more neutrons). Where does the energy come from? Most books I've ever come across simply state $E=mc^2$ and leave it at that. Is it that matter (say a proton or n... |
I'm using the SOFTSUSY package to generate the sparticle spectrum at the EW scale. One of the input parameters is the ratio of the up and down-type Higgs vevs commonly known as $\tan\beta$. The $\mu$ parameter is computed as an output by constraining the Z-boson mass to be compatible with experiment. I was wondering if... |
I need to find the inaccuracies of this computer generated picture, the picture shows a non existent exoplanet. I need to identify the unrealistic features of the planet and its surroundings and write an essay on some of them.
The image is located here: https://i.stack.imgur.com/zXrPy.jpg
Could you help point out some ... |
I'm looking for the most common and accurate approximation functions for III-V semiconductor compounds. So far, I found two (InGaAs as the sample compound):
The simplest one: $E(Ga_{1-x}In_xAs)=(1-x)E_{GaAs}+x \cdot E_{InAs}$
Binomial: $E(Ga_{1-x}In_xAs)=(1-x)E_{GaAs}+x \cdot E_{InAs} - b \cdot x \cdot (1-x)$
For InG... |
Does the mass of projectile affect its trajectory when it is projected in no air resistance environment and why?
|
What is a physical law, a theory, and what is the relationship among them?
I know this is a very basic question, so any reference to epistemology will be greatly appreciated :)
|
I am interested to understand how positive entropy Bose Einstein condensation for cold atoms (say) behave. The way I think about it is as follows: We have an ideal pure state where every atom is in the same ground state which depends on a geometry of a certain trap and the atoms do not interact. Now, naively, I thought... |
If the water were uniform temperature, it would have uniform density, so a bubble should either be all the way at the top (if it's lighter than water) or all the way at the bottom (if heavier). But in reality you don't see this neat separation. Sometimes you see bubbles hovering in the middle.
Is this because the water... |
An opening paragraph:
The usual approach to introducing interactions in quantum field theory
is to make the constraint on the
amplitude of the field towards smaller
values more forceful than harmonic.
For example, instead of the massive
Klein-Gordon field's harmonic
constraint towards smaller field
value... |
How could we measure high energy photons, whithout measuring them ?
I can't understand how we can "see" those Gamma Ray Bubbles if they are not reaching here
In this graph from Nasa you can see those "bubbles" are not reaching solar system:
Then how could be measure that Gamma Ray without the Gamma Rays
Thanks for any... |
There is some convention? how is this 3d to 2d mapping done?
here an example
|
How should I model the tea concentration as a function of time after a tea bag has been submerged? Is there a simple way of measuring the tea concentration?
|
So, one thing has been annoying me ever since I learned about orbital hybridization: you explain the shape of molecules by postulating that the orbitals of multi-electron atoms are linear combinations of the orbitals of the hydrogen atom. Fine.
Here's what gets me, and I've asked several chemistry professors about thi... |
The WIKI Higgs boson site has an interesting diagram illustrating likely Higgs mass intervals that experiments (LEP & Tevatron) or indirect measurements have determined with a 95% confidence level. It posits that the feasible mass ranges are in the intervals of about 115-158 GeV or 175-185 GeV. The Tevatron confirmed t... |
If our universe comes from a flux compactification of string theory over 6 dimensions with a nonzero flux, then it can't be continually deformed to another compactification with zero flux as the total flux is a topological invariant. The cosmological constant of our universe is positive, which in string theory means it... |
Many of the most brilliant ideas of modern physics are very much unpopperian. In view of this, it has become more and more difficult to hold an orthodox Popperian attitude in physics. It simply looks like more of a philosophical dogma nowadays. My question is, should physicists abandon this criterion at least partially... |
Stop me if i'm wrong but displacement is, for example, when you enter a bathtub the water level rises around you.
What happens when displacement isnt possible?
I'll give an example. I have two blocks off steel, one at the top of a chamber and one at the bottom. there is a gap between the two blocks that is filled with ... |
As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. This raises the question of whether there are any processes short of the Big Bang that produce more matter than antimatte... |
Ok, I was just curious but the electromagnetic force can allow paramagnetism macroscopically in some objects. Can this be done microscopically to the subatomic level? Also, what about other forces (besides gravity I'm guessing) meaning the weak and strong force? Strong force being the strongest, would its para- also be... |
"Heat rises" or "warm air rises" is a widely used phrase (and widely accepted phenomenon).
Does hot air really rise? Or is it simply displaced by colder (denser) air pulled down by gravity?
|
Normal-density materials have internal energy, which is the sum of the average energies associated to each of the degrees of freedom. Degrees of freedom can be described as vibrational, translational, and rotational. If you compress this material in such a way that matter cannot escape, you can detect energy escaping i... |
Very unintuitive observation:
I pour myself a Guinness and the bubbles in my glass seem to move down toward the bottom of the glass instead of rising directly to the top of the glass as foam.
How can this be explained? Why is it that I observe this behavior drinking Guinness and not other carbonated drinks? What system... |
Say you have a bottle of water filled up to a height $H$. A small hole is drilled in its side at a height $d$, so that water squirts out. The squirting water travels in an arc as it falls, covering some horizontal distance $S$ away from the bottle before it hits the table top that the bottle sits on. Multi-part ques... |
Even if the double slit experiment gives interesting (weird) results, it only concludes that each photon interacts with itself after passing the two slits. I have been thinking about a different experimental setup, where you have two well defined light sources (with specific wave lengths and phase) but no slits. And no... |
I'm interested in characterizing the behaviour of measures of quantum information in strongly correlated quantum field theories which admit a gravity dual description, e.g through AdS/CFT duality. In a more broad sense, my question points towards the following: in my limited experience, I use to accept that a duality m... |
If double slit experiment is done in a environment with air, then slits could also contain air made up of (approx. 80% nitrogen, 20% oxygen), then there is not empty space inside the slit. How can it affect the experiment? Has it been taken in account?
What are specific requirement to define the slit?
If it were not ... |
I have a doubt about how double slit experiment is made.
Let's think about the perforated wall, what are the requirement for it?
Can a photographic plate could be used as a wall ?
I see a problem here, as a photographic plate serve also as a detector, then the single photon experiment could end up with a single point i... |
In flux compactifications to 4D, e.g. Type IIB on a CY orientifold $X$, one uses fluxes to stabilize the axio-dilaton $\tau$ and the complex structure moduli $z_a$ - the periods of the holomorphic three-form $\Omega$ over the basis three-cycles: $z_a=\int_{\alpha_a}\Omega$, by solving a system of equations for a supers... |
This is a two-part question...
Firstly, models of the specific heat capacity $C$ (i.e. Debye, Einstein) in relation to the temperature $T$ give $C$ as steadily increasing with $T$. I assume that the change in $C$ is due to the heat the system gains being stored in its degrees of freedom- so why doesn't it increase in s... |
How do I find the distance traveled of an object if the speed is not constant?
|
Possible Duplicate:
Homework about spinning top
I have a top with an unknown mass. It has a moment of inertia of 4.00 * 10^-7 kgm^2
a string is wrapped around the top and pulls it so that its tension is kept at 5.57 N for a distance of .8 m.
Could somebody help me derive some equations to help with this? Or to get ... |
It's been claimed that the LHC's 14 TeV energy produces temperatures comparable to that which occurred very soon after the Big Bang. The well-known $E=1.5kT$ formula from classical statistical mechanics predicts LHC produced temperatures in the $2.44\times 10^{17}$ K range. This temperature is much higher than I expect... |
Why does a quantum field theory invariant under dilations almost always also have to be invariant under proper conformal transformations? To show your favorite dilatation invariant theory is also invariant under proper conformal transformations is seldom straightforward. Integration by parts, introducing Weyl connectio... |
Suppose that a someone decided to calculate, for a given amount of heat added into a planet's atmosphere(an ideal gas), how much is the corresponding temperature rising of the atmosphere, $\Delta T$. Assuming that the whole heat transforms into the internal energy of the gas and distributes uniformly (s)he got $\Delta ... |
I'm looking for something to supplement my Physics II class. Last year I started using these video lectures to supplement my Calculus class and it helped tremendously.
I also turned to this educational software when I was stuck in Physics I.
I can't seem to turn up anything similar that deals with Physics II.
I'm prett... |
I stumbled onto this page
http://mylifeisaverage.com/story/1364811/
and the post states that they were
all making strings and shapes with
these sets of 216 really small
spherical earth magnets. What did I
do? I strung them together and found
the string's resonant frequency. It
was 15 Hz
so I'm wondering how... |
In the article Three dimensional gravity reconsidered by Ed Witten, he remarked that the CFT dual to three dimensional quantum gravity has to admit a holomorphic factorization and have a central charge of $c=24k$ for some integer $k$. He argues this by some handwaving from a Chern-Simons crutch even though he admits th... |
Some frequencies of electromagnetic waves are used for transmission of information, like radiowaves, microwaves, light, but some are not..
What about low frequencies?
Perhaps low frequencies aren't used for transmission simply because the waves haven't got enough energy to reach the destination, but it's well-known th... |
Are tidal power plants slowing down Earth's rotation to the speed of the orbiting moon? (1 rotation per 28 cca days)
Are they vice versa increasing the speed of moon orbiting by generating some waves in gravitation field?
If yes, can you calculate how much energy must be produced by how many tidal power plants (compar... |
The phrase "speed of light" is commonly used for the constant c =3E8 m/s, a feature that's "hardcoded" into the structure of spacetime. All massless waves and particles move at this speed, and it's a key concept in all fundamental theories in physics.
Light, in vacuum, is one fine example. But light in air or glass, ... |
Suppose we have 2 systems with the same partition function, does this mean the 2 systems are the same?
For example, in 2D CFTs, would the equality of two partition functions imply that the underlying theories are the same (in the CFT sense, I mean same central charge, same OPE, etc).
Suppose we take the $\text{N}^{th}... |
Fierz identities are discussed in the wikipedia article:
http://en.wikipedia.org/wiki/Fierz_identity
but the article doesn't give any derivation. The article implies that they arise from the blade structure of a Clifford algebra.
Some notes to be deleted after we have a solution:
They seem to arise in QFT calculations... |
I have several question regarding axion. Could anyone give me some brief introduction to what is a axion string, axion field and how is this related to fermion zero mode and chiral zero mode?
|
In quantum chromodynamics, long flux tubes will always snap because a quark-antiquark pair gets created from the vacuum, and hadronization results with a quark attached to each new end.
In string theory, if we try to stretch a single string out a long distance, will it also snap? If open strings with Neumann boundary c... |
If we compare a petrol engine and an electric engine car, it is sufficient for the electric engine car (e.g Tesla Roadster) just to have 1 gear (forward), whereas petrol engine can have up to 7.
Why is it sufficient for the electric engine to have a single gear? Is it because it can deliver the required torque always?
|
Take two identical closed strings, both tracing out exactly the same path in space. These two strings are coincident everywhere. Call this state I.
Take a single closed string following exactly the same closed path as in the first case, but not closing just yet. The string goes around exactly the same path once again b... |
Where can I find a good introductory text for matrix string theory? Most textbooks don't cover it, or only cover it very superficially.
What is the basic idea behind matrix string theory? How can matrices be equivalent to strings?
|
Can one "interpret" Snell's law in terms of QED and the photon picture? How would one justifiy this interpretation with some degree of mathematical rigour? At the end I would like to have a direct path from QED to Snell's law as an approximation which is mathematically exact to some degree and gives a deeper physical i... |
There is well known gravitational redshift of real photons. What about gravitational redshift of virtual photons of charged neutron star? Is electrostatic force become weaker while mass of charged neutron star is growing?
How can electrostatic field of a charged particle swallowed by a black hole escape from the e... |
The Pierre Auger Observatory site mentions the detection of a 3E20 eV (48 J) cosmic ray whose energy, well above the GZK cutoff, was based on an analysis of its atmospheric shower. This was equivalent to the kinetic energy of a baseball with a speed of 79.5 m/s or 177 mph. Of course, cosmic rays with such ulta-high ene... |
I'm interested in knowing if ,in the context of $AdS_{3}/CFT_{2}$, we can (and how to) express the geodesic propagators on the bulk space of the Euclidean $AdS_{3}$ black holes, in terms of meromorphic functions on its conformal boundary $CFT_{2}$.
|
A question in four parts.
What are the main problems which supersymmetry purports to solve?
What would constitute lack of evidence for SUSY at the proposed LHC energy scales (e.g. certain predicted superpartners are not in fact observed)?
Are there alternative theoretical approaches which would address the SUSY prob... |
In general, it seems cosmological theories that encompass more and more of the phenomena of the universe are expected to be more and more mathematically elegant, in conception if not in detail.
Our experience seems to teach that it is a reasonable expectation to assume more fundamental theories will be more "elegant" o... |
A nonuniform linear charge distribution given by $\lambda = bx$, where $b$ is a constant, is located along an $x$ axis from $x = 0$ to $x = L$. What is the electric potential at a point on the $y$ axis? Set potential equal to zero at infinity. Express your answer in terms of the variables given and $\epsilon_0$ (epsi... |
I'm a layman without a university background in physics / math. Since I don't have a background, reading a paper is more of an effort.
Consequently, when I come across an interesting paper, I can't really just give it a glance, and see if it is science, or psuedoscience.
This question is about this paper:
The Schwarz... |
Is there an accepted analogy / conceptual aid for the Higgs field?
In Physics there are many accepted conceptual aids such as
* Schrödinger's cat
* Maxwell's Demon
* I'm sure I'm missing many, but you get the idea
Is there an accepted/standard aid for the Higgs?
I saw a popular treatment of the Higgs boso... |
I am stuck with understanding the following construction. I am breaking it up into segments which I think can be separately answered.
This is related to an earlier question of mine. Note that this previous question was edited a lot after the initial comments came in.
Firstly I would like to know how the following f... |
Consider a rectangular slab of permanently magnetized material. The slab's dimensions are $L_x$, $L_y$, and $L_z$, and the slab is uniformly magnetized in the $\hat{x}$-direction. The slab is not accelerating or spinning. Does the slab generate an electric field?
In a frame where the magnet is stationary, we know $\mat... |
One of my friends has a problem and we don't know how to get this done,
We want to to know the mass of a patient who is laying on a bed. One scales was put under the foot of a bed and weighed 232kg and the other under the head of the bed and weighed 220kg. The centre mass of the patient is 0.8 meters from the foot of t... |
The electron is a particle. The mass of the electron is $9.10938215(45)\times 10^{−31}\, {\rm kg}$.
But why is the mass exactly what it is?
What in physics defines the mass of a elementary particle?
|
Added: 5 times down vote for now! Down voter is this religion or physics, please try to explain your decision.
I'm confused about this.
In physics we know for a vacuum, but I think that there is a contradiction in this term. The quantum fluctuations are the phenomena that contradicts the vacuum existence because, acco... |
How is it possible to encrypt multiple images using fresnel transform and inverse the operation to de-multiplex those images?
|
In general relativity, we use the term "time-like" to state that two events can influence one another. In fact, in order for an event to physically interact with another one, they have to be inifnitely close both in time and space.
As far as I know (correct me if I'm wrong) this principal of "near action/causality" is ... |
Like the order behavior shown in the image, is it due to the universality of some fundamental mathematic theory? Is there some general physics explanation for it?
-
edit: This question comes after I read Terence Tao's talk on universality (pdf).
|
The answer to a previous question suggests that a moving, permanently magnetized material has an effective electric polarization $\vec{v}\times\vec{M}$. This is easy to check in the case of straight-line motion, using a Lorentz boost.
I suspect this formula is still correct for motion that is not in a straight line, bu... |
Here and on many other forums and blogs people ask the question "What if LHC does not find SUSY?". I would like to ask the opposite. What if it finds it? What would the implications be? Is it going to just confirm something understood and expected or is it gong to bring something new? Will there be implications for str... |
In optics it is widely mentioned real images are projectable onto screens whereas virtual ones can only be seen by a person. Isn't that contradictory? I mean in order to see the virtual image it has to be projected onto the retina (ultimately acting as a screen).
So, why can you see virtual images in the first place... |
I understand the reason that bicycle pedals are oppositely threaded on either side. What I don't understand is why it works because I'm missing something.
Take the right pedal for example. It's threads are right-handed, so it would be tightened by turning it clockwise (if the pedal were in between you and the bike). No... |
I just watched [some BBC show] where the host talked about Arrow of Time, where by 2nd law of thermodynamics states that "nature" is always low entropy to high entropy OR "ordered/structured" to "unordered/unstructured" state.
The "intiutive" examples used, also found elsewhere, are events like iceberg "spontaneously" ... |
For a $c=1$ Boson on a circle at the self-dual rdius, we get an enhanced gauge symmetry $\hat{SU}(2)_1$. It is said that we can orbifold this model by any finite subgroup of $SU(2)$ since $SU(2)$ is a symmetry of the model. But the Lagrangian of a $c=1$ Boson does not have an $SU(2)$ symmetry even at the self-dual radi... |
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