What is String: Definition and 1000 Discussions

In molecular biology, STRING (Search Tool for the Retrieval of Interacting Genes/Proteins) is a biological database and web resource of known and predicted protein–protein interactions.
The STRING database contains information from numerous sources, including experimental data, computational prediction methods and public text collections. It is freely accessible and it is regularly updated. The resource also serves to highlight functional enrichments in user-provided lists of proteins, using a number of functional classification systems such as GO, Pfam and KEGG. The latest version 11b contains information on about 24,5 million proteins from more than 5000 organisms. STRING has been developed by a consortium of academic institutions including CPR, EMBL, KU, SIB, TUD and UZH.

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  1. B

    Archived Centripetal Acceleration and string tension Question

    Homework Statement A 6.0kg object is attached to two 5.0m-long strings and swung around in a circle at 12 m/s. Determine the tension in the two strings, and explain why the tensions are not the same. Given: m=6.0kg v=12m/s length of string= 5.0m Homework Equations ƩF=m.a ac=v^2/R...
  2. P

    Collision with 3 particles and inelastic string

    The problem : 3 identical balls lie on a smooth horizontal surface, the 3rd ball moving with a velocity v while the other 2 are stationary and inter-connected via a taut inelastic string. Ball 3 strikes ball 2 normally making angle = 30 degrees with the string. Energy is conserved. We need to...
  3. T

    1 string, 2 balls, motion problem

    Homework Statement http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Mathematics%20%289709%29/9709_w09_qp_41.pdf number 6III...
  4. N

    Assembly how to check empty string?

    I am asking user to enter a number if user hits enter key instead of entering a value then i need to exit the program. see code below ; i put the value into eax cmp AL,0 ;i compare is al reg is empty je exitProgram ; some instructions exitProgram: Invoke ExitProcess,0 Public...
  5. M

    Electric Quadrupoles, Micro Black Holes & String Theory

    I had an exchange with Lubos Motl about this topic, in the comments here. Very briefly, there is a 2004 paper in which the author (Kjell Rosquist) considers the old idea that the electron is actually a spinning, charged (i.e. Kerr-Newman) micro black hole. Using a purely classical model for...
  6. B

    Use differentials to estimate the change in tension of yo-yo string

    . Homework Statement The tension T in the string of the yo-yo is given by: T=(mgR)/(2r^2+R^2) where m is the mass of the yo-yo and g is the acceleration due to gravity. Use differentials to estimate the change in tension if R is increased from 3cm to 3.1cm and r is increased from 0.7cm...
  7. F

    Quantum theory vs String theory (Who's the best?)

    Just about few hours ago,my friend and i argued about which theory is the best theory nowadays ever existed. I claim that string theory is the only game in town as what i heard from Dr. Michio Kaku's TV shows, while my friend strongly disagree with it. He claimed that quantum theory is the best...
  8. P

    Fortran [Fortran] String variable for output filenames

    This is the troublesome part eLeftOutFile = 'data/ElonL'//fileNameSuffix(0:25)//'.dat' OPEN(754,FILE=eLeftOutFile,STATUS='REPLACE',ACCESS='SEQUENTIAL') First off, fileNameSuffix is a CHARACTER(len=40) just to be safe, I am just cutting it off, since those are the relevant parameters...
  9. O

    What is the Speed of the Lowest Bead as the Upper Bead Passes Over the Peg?

    Homework Statement A massless string having three beads of identical mass attached to it is placed so that it hangs at rest on a thin frictionless peg, as shown. Of course, the string then slides over the peg and falls to the ground. If h = 55 cm, what is the speed of the lowest bead at the...
  10. R

    What is the tension in the string?

    Homework Statement "What is the tension in the string?" .5kg block Suspended at the midpoint of a 1.25m-long string Ends of string attached to ceiling are 1m apart.Homework Equations cosθ, sinθ, tanθ T_1_x+T_2_x+F_g_x=ma_x T_1_y+T_2_y+F_g_y = T_1_y+T_2_y- F_g = ma_xThe Attempt at a...
  11. AJKing

    Acceleration for Masses on a slope/plane connected by a string

    I think I've solved this, I'm looking for an answer check. Homework Statement Given the picture above, find the acceleration of the block and the tension in the string. Assume the string preforms ideally and the pulley is frictionless. Homework Equations Fnet = ƩFx + ƩFy = maThe Attempt at...
  12. T

    Tension on a string between two masses.

    Homework Statement The figure below shows an object of mass m1 = 1.1 kg on an inclined surface. The angle of the inclined surface is θ = 31° with the horizontal. The object m1 is connected to a second object of mass m2 = 6.10 kg on a horizontal surface below an overhang that is formed by the...
  13. I

    What is the maximum weight a string can hold before breaking?

    I don't know much about physics but I know some math. So say I want to set up an experiment (hopefully easily reproducible) where I have a string (I can find out what I like about the string) tied to a spot above the ground. It is hanging straight down. Say I tie a zip lock back to it and I...
  14. P

    Find plane's acceleration from mass on a string

    Homework Statement A pendulum has a length L = 1.13m. It hangs straight down in a jet plane about to take off as shown by the dotted line in the figure. The jet then accelerates uniformly, and while the plane is accelerating, the equilibrium position of the pendulum shifts to the position shown...
  15. P

    Can Swinging a Shotgun Affect the Shot String Spread?

    Homework Statement i apologies in advance if this is not posted in the correct section but it seemed the most like basic physics to me. Well i have a question that i need help answering for my own enjoyment.I am an avid Shotgun Shooter and all through out my live i have always been told...
  16. A

    What is the difference between string that make phontons and proton?

    according to the string theory, what is the difference between the strings that make the photons and the strings that make the protons? photons don't have mass and protons do, does it all ultimately rely on simply how the strings vibrate, or what? do photons' strings have lowest energy possible...
  17. H

    Tension in a light inextensible string

    Homework Statement The attachment shows the string which is light and inextensible passing over two pulleys which are NOT massless. Hence they have some mass and some Moment of inertia. There is no friction in the pulley thus the pulleys are free to rotate. K ≥ 1 we know that the...
  18. R

    Circular mgomentum - Tension of a string.

    Circular momentum - Tension of a string. Homework Statement A body of mass 1kg is tied to a string and rotates on a horizontal frictionless table. If the length of the string is 40.0 cm and the speed of revolution is 2m/s, find the tension in the string. 2. The attempt at a solution...
  19. K

    Wave on string, bdry cond is mass on spring

    Homework Statement A semi-infinite string (constant tension T and density ρ) lies along the positive x-axis. The motion of the string is described by the linear wave equation \begin{equation} h_{xx}-c^2h_{tt}=0 \end{equation} with c² ≡ T/ρ, where h(x,t) is the transverse displacement...
  20. M

    Why does rotating a ball on a string faster makes it horizontal

    Hi suppose i had a ball on string and started to rotate it in a circle around my hand. When i increase the speed of the ball it becomes more and more horizontal. The only forces i can think of at play is centripetal and centrifugal forces and the force exerted by my hand and gravity. Is somehow...
  21. S

    Compressive force on a cylinder wrapped with a string

    Hello everyone, I'm working with a design team to take quick and accurate measurements of the middle upper arm circumference in third world countries to assess malnutrition in children. One of the issues in taking measurements is people pulling variably on the tape measure around the arm. My...
  22. T

    Trying to understand Quantum Entanglement, String Theory, and the BB

    Consider me physics illiterate since my last class was advanced placement physics in high school (over 20 years ago). I am trying to understand what the title says, How does quantum entanglement, string theory, and the BB fit together? Skipping to the meat of the subject, everything revolves...
  23. D

    Electrostatics: Using a conducting string suspension.

    Homework Statement This is a lab question. Basically what the lab entails is we have two spheres. One is suspended from a string and another is attached to a non-conducting rod. We inductively charge the sphere attached to the rod. Then we bring it close to the other sphere that is being...
  24. U

    Why does a stone tied to a string not fall?

    when we tie a stone to a string and spin it,it does not seem to fall.why does it happen?i mean to say that,no matter how great its horizontal velocity and centripetal force is,the vertical component of the acceleration won't be affected.it means that the stone should keep falling no matter how...
  25. C

    Acceleration of two masses on string

    Homework Statement In the Atwood's machine below the string passes over a fixed cylinder of mass mc. The cylinder does not rotate. Instead, the string slides on its frictionless surface. (Use any variable or symbol stated above along with the following as necessary: m1, m2, and g. Find the...
  26. S

    Calculating the tesion in a string holding a 1 meter stick

    A meterstick (L = 1 m) has a mass of m = 0.13 kg. Initially it hangs from two short strings: one at the 25 cm mark and one at the 75 cm mark. What is the tension in the left string right after the right string is cut? Calculating the free body diagram where we put the acceleration...
  27. J

    String Theory: Is Energy a Physical Entity?

    I was watching a video on string theory and they claim that its all vibrating strands of energy. I thought energy was just a property of the system, not a physical entity. So do they mean something else by "energy"?
  28. Dembadon

    Comp Sci Programming in C++: 3D array string copy

    Homework Statement I am making a Klondike style solitaire game, and I am trying to load a string into a 3D array. I am representing the "Tableau" with a 3D array (we haven't gone over structs yet). I want to represent the spaces which don't have cards with the word "empty". I'm not...
  29. K

    Can we write equations for strings in pulley systems?

    Ofcourse we can write the equations for blocks on a single fixed pulley taking the tension upwards and weight as downwards and then equating according to the acceleration. Can we write equations for the string (massless or with mass)?
  30. tom.stoer

    AdS/CFT and non-perturbative gravity in string theory

    I understand that suitable compactified strings in AdS correspond to conformal field theories (w/o gravity) living on the boundary space. What I do not get is the exact relationship between non-perturbative gravitational phenomena in the bulk and the CFT. All what I have seen are...
  31. A

    Can We Pull a Metal Ball Out of a Black Hole With a Steel Cable?

    There is a spaceship situated orbitting a black hole at x million miles. We have an exactly x milllion mile long string (perhaps a bit longer) Lets not call it a string, but a flexible steel cable instead. Now, we tie a metal ball at its one end, and project the ball towards the black hole...
  32. J

    So im a little confused about string theory will give us unification

    Could someone give me a short summary(if possible) of how discovering matter is made of vibrating energy will give explanation to all four fundamental forces?
  33. J

    Will string theory explain what electric and magnetic fields really are?

    I mean we really don't know what they are, right? We just know they can be positive or negative, north or south, but we really don't know why they exist. Will string theory give a definite answer to this? And also gravity. Will it confirm Einsteins theories?
  34. M

    Puzzled about circular motion (whirling a bung on a string)

    Dear forums Hello. I teach physics, and whilst I think that my knowledge is fairly sound, once every now and I then I encounter something which baffles me like so... In a simple demo of circular motion, a rubber bung is whirled around the head in a horizontal plane. If the bung is...
  35. Q

    Infinitely long piece of string.

    Not sure if this is a topology question but here goes. Imagine an infinitely long piece of string and I cut it in half with a pair of scissors. Both pieces are still infinitely long but I'm now stood at the ends of infinitely long strings, how can I be at the end of something with infinite length?
  36. J

    A question about a vibrating string

    Homework Statement "Vibrato" in a violin is produced by sliding the finger back and forth along the vibrating string. The G-string on a particular violin measures 30cm between the bridge and its far end and is clamped rigidly at both points. its fundamental frequency is 197Hz (a) how far...
  37. K

    Find sound wavelength from a vibrating string

    Homework Statement Sound Wavelength From String During a concert a pianist hits a key that sets up a standing wave in a piano string that is vibrating in its fundamental mode. The string is 0.5 m long, has a mass density of 0.002 kg/m and is held under a tension of 120 N. What is the wavelength...
  38. A

    Hinged rod attached to elastic string

    A rod (mass M, length L) hinged at point X. End Y is attached to X by an elastic string passing over a pin P, the natural length of the string is L. P is a distance L from X. Elastic Modulus of string: (1/4Mg) Refer to GPE to X and prove that total PE is: (1/4)MgL(1-cosθ-2sinθ) and find...
  39. P

    Easy question on CFTs in string theory

    Hi, I have a question concerning simple bosonic string theory governed by the Polyakov action. Under which assumptions/requirements is the corresponding worldsheet theory a conformal field theory? Is this always true or does it depend on the topology of the worldsheet? Conformal symmetry of...
  40. X

    Can anyone explain to me what is string theory mathematically?

    Can anyone explain to me what is string theory mathematically?
  41. E

    Velocity & Frequency Wave on String

    Please help me, I'm so bewildered it's not even funny. Does the frequency only depend on the source? This all seems so paradoxical to me...for example: An 100 Hz oscillator produces a wave on a rope with a wavelength of .1 meters. If I increase the tension of the rope by sticking a weight at...
  42. B

    How do nodes on a string produce tension if they are stationary?

    The vibration in a string is caused by the tension force on point masses inside the string : The tension force itself results from "the net electrostatic attraction between the particles in a solid when it is deformed so that the particles are further apart from each other than when at...
  43. R

    Theoretical Mono Poles, String Theory

    Hi all, Would like to start off by letting you all know i am new to the PF and the reason for joining is due to constant ideas and thoughts flooding my brain to no end, i do not have any physics degree's but i do share an intense interest in Physics. According to a friend of mine the only...
  44. Q

    How are strings allowed to vibrate in string theory?

    I have recently been reading up on the basics of string theory and my question is this. How exactly are strings "allowed" to vibrate? In particular, do they have to be in all ten dimensions of space as predicted by M-theory at once? Or can they just "reside" in several of those dimensions...
  45. G

    String theory gets you any result you want

    It's really difficult as a layman trying to find out who is right and wrong in this debate as far as string theory. I find it kind of hard to believe that string theory is just simply completely wrong and has no relevance whatsoever to reality. After all so many theorists and so many papers...
  46. A

    Mind-boggled by the string theory

    Hi. I am fairly new to physics. I have recently read the first half of a book by Michio Kaku called “Beyond Einstein”, and I am really struggling to get my head around the superstring theory. The superstring theory seems illogical for the following reasons... 1. Nature demands symmetry. So...
  47. A

    Two blocks, a string, and a spring.

    Homework Statement Two blocks A and B with respective masses m_{A} and m_{B} with respective masses m_{A} and m_{B} are connected via a string. Block B is on a frictionless table, and block A is hanging at a vertical distance h from a spring with spring constant k that is at its equilibrium...
  48. N

    String Theory from deterministic automaton

    Gerard 't Hooft just dropped this interesting paper. http://arxiv.org/abs/1207.3612 Discreteness and Determinism in Superstrings Gerard 't Hooft Ideas presented in two earlier papers are applied to string theory. It had been found that a deterministic cellular automaton in one space- and one...
  49. M

    Is String Theory worth the resources it's taking?

    Now obviously String Theory has been responsible for some valuable research, and even if the theory were completely disproven (although I don't see how; my understanding is that it is still too vague in it's predictions and descriptions to be proven or disproven conclusively). But String Theory...
  50. C

    Sound/accoustics - guitar string question

    (I hope this is the right section). For those who play guitar, you might have noticed that plucking the open 1st string (E) causes the 5th (A) string to vibrate. Why is that? It doesn't happen with any other string/note that I'm aware of. I'm sure there's a physical explanation for it. :confused:
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