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. R

    Three masses, a string and pulley and a table -- solve for the acceleration

    Let T be the tension in the string, a be the acceleration of mass 2m, 2a be the acceleration of mass m T = (m) (2a) ---eq(1) The mass 3m will come down with acceleration a’ = (a+2a)/2 = 3a/2 3mg - 2T = 3m . 3a/2 from equation 1 3mg - 2(2ma) = 3m . 3a/2 thus a = 6/17g thus acceleration of 3m...
  2. K

    Finding the depression and the tension of the string

    I would assume that all the tension in the wire originates from the weight of the mass, and is equal to ##T=mg##, but that is incorrect. Forming a right triangle with a hypothenuse denoted by ##x## and applying Pythagoras theorem: \begin{cases}x^2=y^2+l_o^2 \\ x+y=l_o+\Delta l\end{cases} Solving...
  3. Vamsi9955

    B How can string theory be proved

    The fundamental building blocks of the universe is thought of super strings, if proved can solve the mysteries of the universe but if proved than how? And how can it solve the mysteries of dark energy &dark matter and black holes?
  4. L

    Finding the path of an oscillating string

    Problem Statement: The amplitude of the undamped oscillation of the point of the string is 1 mm, and the frequency is 1 kHz. What path will pass a point of 0.2 minutes? Relevant Equations: V=f x lamda I don't understand the question. Please help
  5. Another

    1-D wave resonance in the case of an Open-Ended String

    ## \frac{1}{v^2} \frac{∂^2y}{{∂t}^2} = \frac{∂^2y}{{∂x}^2} ## and general solution ## y = A sin(kx+ωt)+ B cos(kx+ωt) ## http://blogs.bu.edu/ggarber/archive/bua-py-25/waves-and-sound/standing-waves-in-strings-and-pipes/ In case fixed at both ends The condition is ##y(0,t) = 0 ## and ##y(L,t) =...
  6. A

    A statics problem with a mass on the end of a string

    I have this problem. I know G, alpha and mu. I need to know theta for equilibrium. My problem is that in place of the thread I need to have a tension and when i write the equations of forces on all 3 axes and then I apply the conditions that Ff<=mu*N (Ff-friction force, N-normal on plane...
  7. B

    Bodies connected by a light inextensible string on an inclined plane

    Here is the question (Qu 9): Here is what I have attempted: assumed that the accelerations are equal, found a value for the acceleration, thus worked out the time taken for A to reach the bottom. then assumed that the tension becomes 0 once A hits the floor, and then worked out B's new...
  8. S

    A Is M-Theory more fundamental than String Theory?

    M-Theory is a theory of membranes which are the fundamental objects of the theory (M2 and M5 branes), however these objects are considered solitons, solutions of supergravity. How can membranes be "fundamental" if they are solitonic solutions of supergravity? Or am I missing something? And is...
  9. P

    I Electrostatic in string theory or LQG

    How the repulsion between electrons occurs in String theory and in the loop quantum gravity? The electrons will also create electrostatic fields, or will it be the another mechanism?
  10. M

    Force on a pin from a pendulum and a string

    1. Determine the velocity of the ball when it is 30degrees from the horizontal: U1 = mgh = mg(0.8m) U2 = mgh = mg(0.4+0.4cos(30)) = mg(.74641) ΔU = U2 - U1 = mg(.74641 - .8) = mg(-0.051433) T1 =0 T2 = 0.5mv^2 ΔT = T2 - T1 = 0.5mv^2 ΔU = ΔT mg(-0.051433) = 0.5mv^2 ====> v = 1.025394 2. Use...
  11. J

    I Does String Theory Justifiably Extend Gravitational Laws to Sub-Planck Lengths?

    I posted this earlier, but the thread has been closed. String theorists frame much of their studies in the context of Planck length. The theories are meant to fold together QM and general relativity. The equation for Planck length includes the gravitational constant, G. It seems to me the...
  12. J

    I The Planck length and string theory

    String theorists frame much of their studies in the context of Planck length. The theories are meant to fold together QM and general relativity. The equation for Planck length includes the gravitational constant, G. It seems to me the theorists are assuming the gravitational laws extend to...
  13. A

    What is the work done on cart by the string?

    Homework Statement A cart of mass M1 = 6 kg is attached to a block of mass M2 = 3 kg by a string that passes over a frictionless pulley. The system is initially at rest and the table is frictionless. After the block has fallen a distance h = 1 m: What is the work Ws done on the cart by the...
  14. B

    Pulley question -- Two unequal masses hanging by a string

    Homework Statement Homework Equations F=ma The Attempt at a Solution Okay, so this is probably a really dumb question, but I'm stuck for some reason on it. I drew free body diagrams for each block. For B, there's a small downward arrow for gravity, and a large arrow for tension. For A...
  15. S

    Motion of masses connected by a string over a pulley

    Homework Statement Two particles A and B of masses m and 2m are attached to the ends of light inextensible string which passes over smooth fixed pulley. The particles are released from rest and when particle B has moved h meters, it hits the ground and does not rebound. (i) Find the speed of...
  16. R

    Help me understand this question -- "Three consecutive zeros" in a binary string

    Homework Statement How many bit strings of length eight contain either three consecutive 0s or four consecutive 1s? Homework EquationsThe Attempt at a Solution This might sound dumb, but would the eight bit string of all zeros satisfy the conditions on the question? I understand its asking for...
  17. R

    PhD Inquiry, Modified Gravity or String Theory

    Hello everyone, I am currently finishing my Masters in Theoretical Physics and looking forward to continue in a PhD. I always thought I would love String Theory, and now that i am actually doing it I see that my feeling was correct. I do not know why but trying to understand its concepts...
  18. J

    A De Sitter Vacua in String Theory and KKLT

    Earlier in the forum Urs Schreiber discussed criticism of KKLT, and claims that string theory does not allow de Sitter vacua https://www.physicsforums.com/threads/no-metastable-type-iib-de-sitter-vacua.950271/ The following recent claims to address these concerns, and claims KKLT allows de...
  19. A

    I Alternative approach to analyzing a massless string

    Consider a massless string which can rotate about a fixed pulley (first picture). The coefficient of static friction is μ. Assuming that the motion is impending, the goal is to find the equation that describes the variation in tension of the string. ( T2/T1 = eμΦ where Φ is the subtended angle.)...
  20. F

    Standing waves on a string experiment -- Relative amplitude of harmonics

    Hello forum, I am wondering why the higher order (higher harmonics) standing waves developed on a string under tension generated by an oscillating mechanical vibrator (set at the same amplitude but with variable frequency) have lower amplitude when compared to the lower harmonics (the...
  21. T

    Describing the Motion of a String at the Antinodes

    Homework Statement How would you describe the motion of a string at two adjacent antinodes? Homework Equations N/A The Attempt at a Solution So would the antinodes not be moving since it's a standing wave? Or would they be moving in phase because they are propagating together?
  22. alantheastronomer

    A Can String Theory Explain Fundamental Particles Through Standing Waves?

    I've heard in a general way that string theory can describe the properties of the fundamental particles through standing waves or resonances of strings. Is this in fact the case, and if so, can someone provide a link to the relevant research papers?
  23. W

    I Probability that a Random String is a Word

    Hi, Say L is a human language (e.g. German, Chinese, etc.) and w is a string in L of length n>1. Is it known for different languages what the probability is that w is a word in L? And if S is an ordered set of strings, the probability that S is grammatically correct in L? I mean, I know or have...
  24. physics_cosmos

    Dynamics of a string coupled pendulum

    Homework Statement My problem/task is to explain in elementary terms the dynamics of a string coupled pendulum, the same as in this diagram: Is it simple to make a free body diagram for the pendulums? Is it possible to understand the motion as being caused by SHM oscillation of the top...
  25. K

    I Fundamental equation in string theory

    Is there a fundamental equation in string theory and can it be derived from a variational principle?
  26. Oklid

    'Force on pulley by a string' conception

    Homework Statement In the figure below is shown the system below are shown two blocks linked by a string through a pulley, where the block of mass m1 slides on the frictionless table. We assume that the string is massless and the pulley is massless and frictionless. Show the forces ( as...
  27. H

    Initial displacement of a midpoint of a string?

    Homework Statement Then we are asked to determine the initial discplament, velocity and acceleration of the midpoint of the string. Homework Equations I guess we should use equation x(t)=Asin(wt+phi) The Attempt at a Solution My attempted solution is to use the above equationa and put t=0...
  28. thebosonbreaker

    Resolving forces: Mass on a string

    Homework Statement A mass of 50 grams hangs in equilibrium on a string. The mass is pulled aside and upwards by a force of 0.3N which makes an angle of 30° with the horizontal. Find the angle that the string makes with the vertical and the tension in the string. Homework Equations Body is in...
  29. M

    Finding tension of a string spinning horizontally

    Homework Statement Spin 340 gram mass at the end of a 72 cm string in a horizontal circle around head 2.5 rev/s. Calculate tension Homework EquationsThe Attempt at a Solution I know tension might be equal to mass times centripetal acceleration, but I’m not sure
  30. Loubrainz

    Waves on a String -- Minimizing reflections from the far end (ring on a bar)

    Homework Statement A string of linear density ρ terminates in a small ring of mass m. A horizontal bar is passed through the ring, perpendicular to the direction of the string at rest, and the string is stretched to a tension T. Friction between the ring and the bar generates a resistive force...
  31. S

    Circular Motion: Swinging a rock on a string in a vertical circle....

    Homework Statement :[/B] One swings a rock at the end of a string. We wish for the string to remain taut and for the rock to travel in a circulat path, in a vertical plane. What mathematical condition must the centripetal acceleration of the rock satisfy for the string to remain taut when the...
  32. W

    Studying Mathematics to Understand String Theory/SuperString

    I just recently graduated with a mathematics degree. Lately, I've been very fascinated with quantum mechains and string theory, but when I try to do research I am a little overwhelmed by all the varying topics of advanced mathematics I have to know. Can anyone suggest mathematical topics to...
  33. Zakiyah Afrin

    What will the wave velocity be in this string?

    Homework Statement What will be the wave velocity, if a string of 100 cm length is in a 10 kg-wt tension forms 9 nodes when vibrated and becomes symphonic to a 50 Hz tuning fork. Given, Cross sectional area of string, $$A=4.95 mm^2$$ & density, $$d = 0.25 g/cc$$? Homework Equations $$...
  34. opus

    Python troubles- says I'm using a string in arithmetic

    Homework Statement I'm making a program to display what I have posted in the image and my program needs to look just like it. The idea is to have an employee enter information such as their pay and hours worked. Then taxes get calculated and it shows a net amount that the employee has made for...
  35. J

    A Is Bohmian Mechanics incompatible with String Theory

    Bohmian mechanics requires a preferred reference frame. But String theory doesn't have any preferred frames, so isn't BM incompatible with ST?? Maybe it would be compatible with other theories of quantum gravity that permit a preferred frame (LQG, CDT)...
  36. prashantakerkar

    I How have changes in table tennis racket design affected the game?

    https://en.m.wikipedia.org/wiki/Table_tennis_racket Would like to know the impact for the table tennis game if the racket is changed to a String type Lawn tennis or Badminton racket? Thanks & Regards, Prashant S Akerkar
  37. Spinnor

    I Masses of Fermions, string theory, Higgs mechanism

    Take the first family of fundamental fermions, u, d, e-, and ν. The u and d are more massive than the e- and the e- is more massive than the ν. The u and d interact via 4 forces, the e- interacts via 3 forces, and the ν interacts via 2 forces. The fermions that interact via the most forces are...
  38. alexi_b

    Radial Acceleration on a string

    Homework Statement A ball on the end of a string is whirled around in a horizontal circle of radius 0.250m. The plane of the circle is 1.06m above the ground. The string breaks and the ball lands 1.90m (horizontally) away from the point on the ground directly beneath the ball's location when...
  39. A

    A What exactly is the string theory landscape?

    Do the the different calabi-yau space solutions of strings theory exist is isolated space-times or are they a part of a continuous whole with space folding and unfolding as you move though space?
  40. E

    Proof by Induction of shortest suffix of concatenated string

    Homework Statement Wherein α, β are strings, λ = ∅ = empty string, βr is the shortest suffix of the string β, βl is the longest prefix of the string β, and T* is the set of all strings in the Alphabet T, |α| denotes the length of a string α, and the operator ⋅ (dot) denotes concatenation of...
  41. P

    Rotational mechanics string wrap around twig

    A mass m is tied to a string which is wrapped to a twig of a tree. How many minimum times should we wrap the string so that it doesn't fall? Here is what i got... 1.There is friction between the twig (or fixed cylinder) and the string. 2. if the total friction between the string wrapped around...
  42. E

    Proof by Induction of String exponentiation? (Algorithms)

    Homework Statement Wherein α is a string, λ = ∅ = the empty string, and T* is the set of all strings in the Alphabet T. Homework Equations (exp-Recursive-Clause 1) : α0 = λ (exp-Recursive-Clause 2) : αn+1 = (αn) ⋅ α The Attempt at a Solution [/B] This one is proving difficult for me. I...
  43. Akshaya dhakal

    B Help with a string theory equation

    This is related to string theory
  44. S

    Understanding Waves on a String

    Hello I am having trouble understanding why the horizontal component Fx is equal to the F for a wave on a string I am trying to understand Energy in wave motion. The picture attached is a representation of my problem. My textbook tells me that this is because it is a transverse wave which means...
  45. A

    B Is string theory a deterministic hidden variable theory?

    There are several interpretations of QM which differ from being deterministic or non deterministic, with or without hidden variables and local or non-local. As I understand it ST poses the existence of vibrating strings, that is, physical objects with definite properties, moving along a world...
  46. tatkhj

    How do the Mobius and Klein models illuminate string theory?

    I'm a speculative fiction writer and playwright, a retired archirect with a master of architecture degree in theory, and a theater producer, director, and acting improvisor. I'm currently working on a TV series of 169 episodes exploring life in a contemporary parallel universe very much like...
  47. PGaccount

    B Exploring String Theory: Open and Closed Strings

    are open strings like world lines? and closed strings like loops?
  48. H

    Which powers works on bead on a string?

    Homework Statement I know that a bead is threaded on an metal sring (no T), and the bead is not moving/ The metal string moves in circular motion at a slope of 60 degrees. The string moves one spin in one second/ which powers works on the bead? Homework EquationsThe Attempt at a Solution
  49. bhobba

    B Is String Theory Built On Funny Math?

    In asking a question about analysis textbooks there was a bit of a chat about things like S = 1 - 1 + 1 - 1 ... = 1 - (1 + -1 +1 -1 ...) or 2S = 1 or S=1/2. I will say straight away the answer to what's going on - what infinite sums are, are simply definitions and believe it or not there are a...
  50. A

    Harmonic Frequency of a String

    Homework Statement A string (m = 1 kg) fixed at both ends is vibrating in its second harmonic mode. If the length of the string is 2 m and it feels 50 N of tension, which of the following is NOT a possible harmonic frequency for this string? a) 1.25 Hz b) 2.5 Hz c) 5 Hz d) 10 Hz e) 20 Hz...
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