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. LCSphysicist

    String hanging and oscillating

    I thought we could do the part a by two steps: (Studying the motion along x {there is no}) and along y (Here should be T + dT)****** But apparently the answer is: "" So i think if the answer is wrong or, if not, where i made a mistake?
  2. burian

    Trajectory of a mass element in a string overhanging a pulley

    Hello everyone, this is a thought experiment I made, it involves two ropes being pulled of a pulley similar to an atwood machine, and a block attached to the two pulleys at the other end. The ropes are being pulled at a constant velocity $ U$ from the end away from the block and the block rises...
  3. M

    How do I read this equation for air friction/drag on an object?

    I am trying to understand an excerpt from an article describing the vibrations of a string (eg. guitar/piano) which reads as follows: This is basically the wave equation with Δm representing a small piece of mass from an interval of the string and two forces added to the right side. He...
  4. LCSphysicist

    Total energy of the normal mode on a string

    What you think about this question? Seems a little strange to me, that is, it considers the maximum kinetic energy when the displacement of the oscillators is maximum, i don't think this is right.
  5. A

    B Size of strings in string theory

    Quite a long time ago, I read about length of strings in string theory. And, if I remember correctly, expected length was in light years. I looked at Wikipedia today, and I see currently expected length of string is very small, around Plank size. Is it changed over time, or the expected length...
  6. LCSphysicist

    Fundamental frequencies in a violin string.

    Why is this wrong?: That is, why is not f = 4fo? Oh. And my figure 1 can be wrong, because maybe i got confused if the string was open or closed in the boundaries, anyway this change nothing the relations (1)
  7. Abdullah Almosalami

    Question about Waves on a String

    Summary:: Could you send a second wave pulse down a string that would overtake an earlier wave pulse? Got this question in my physics textbook. Ignoring reflection (i.e., you had a very long string), say you send a transverse wave pulse down a string fixed on its other end to a wall. Could you...
  8. T

    A Cosmic string and vacuum decay

    https://arxiv.org/abs/2002.04856 It's proposed that topological defects like cosmic string enhance vacuum decay. I do not quite believe it.
  9. John100861

    David Morin classical mechanics Problem 2.6: Disk held up by a massless string

    The first part is easy, we have 2T= Mg T= 0.5 Mg Now for the second part where I'm having trouble understanding Morin's solution: I take the normal force on a small circle arc to be N, we know that the y component of the normal force must be balance with Mg for the whole disk, therefore Ny =...
  10. Z

    Lagrange equations: Two blocks and a string

    I've problems understanding why the kinetic energy of the string is only $$T_{string}=\frac{1}{2}m\dot{y} $$ Why the contribution of the string in the horizontal line isn't considered?
  11. P

    A string over a pulley with two hoops wound like spools on each end

    I have seen the solution to this problem but I don't understand it. Here is my drawing of the problem. Apparently I should do the sum of the forces and sum of the torques for both hoops like this: hoop 1: (1) τ - M1g = M1(a1t-a1R) (2) τR1 = ½M1R12a1r/R1 hoop 2: (3) M2g - τ = M2(a1t+a2r) (4)...
  12. J

    B String Theory & Elementary Particles: What's Real?

    If string theory is correct does it mean that elementary particles like photons, electrons, and quarks don't really exist or does it mean they do but are made of cosmic strings and so therefore are not elementary?
  13. A

    Comp Sci Troubleshooting String and sscanf in C: How to Get Correct Output | Example Code

    #include<stdio.h> int main(){ char str[]="My first book"; char *a,*b,*c; sscanf("%s %s %s",a,b,c); printf("a=%s b=%s c=%s",a,b,c); } I want the output: a= My b=first and c=book. But it does not work, why?
  14. MathematicalPhysicist

    A Is Stochastic String Theory the Key to Original Ideas in Physics?

    Well there was today some lecture on String theory which I got late since I was reading something else in Condensed matter physics and then I looked at a book that I have of stochastic Integration with jumps and by associativity of ideas I searched google for Stochastic String Theory and got to...
  15. H

    Calculating Period of System with Masses, R & dX

    Here is the picture on the system. I have to find the period (T). The masses, R and dX is given. The systam at first is at rest, then at t = 0 we pull the plank to dX distance from its originial position. In the thread...
  16. Diku Khanikar

    Waves and vibrations on a string

    Q.1. The length of a stretched string fixed at both ends has a length of l=10 cm, mass per unit length ρ= 0.01 gm/cm. If the tension ' T ' is produced by hanging a 11 kg weight at both ends of the string, then calculate, a) The wavelength of the first two harmonics, b) The speed of the wave...
  17. P

    Find the tension in the string of this two mass system

    I know that it will probably execute something similar to circular motion. I thought of conserving momentum but I think there is an external force being applied due to the impulse which will prevent me from doing so. I know that once I find the tension it would become very easy to find the...
  18. Zouatine

    What units for the wave function of a string?

    hello , hope all of you are doing well , i have question about the unit of the function of waves of string fixed in both boundary , the function of waves is function of two variables x and t , so it's function describe the displacement in function of place and time , Ψ(x,t)=φ(x)*sin(ωt+α)...
  19. T

    Two blocks connected with a small string pulled up a ramp by string

  20. R

    Waves Homework help -- Waves on a String

    Okay well I'm stuck on this one. I know that lamba times frequency is wave speed and 1/f is period. I think that the wavelength of the wave is four but what is the frequency? (1/2)? Would I multiply 4*1/2 to get 2 m/s as the wave speed and then if the frequency doubles to .25, the wavelength be...
  21. M

    Wave Equation: d'Alembert solution -- semi-infinite string with a fixed end

    Hi, I was trying to get some practice with the wave equation and am struggling to solve the problem below. I am unsure of how to proceed in this situation. My attempt: So we are told that the string is held at rest, so we only need to think about the displacement conditions for the wave...
  22. C

    Standing Waves Homework: A Tuning Fork, a String and a Hanging Mass

    Hi guys, so I am struggling on the Standing Waves concept. I understand that these are waves that move in place but I don't know how to attempt this problem. Can someone set me on the right track?
  23. B

    Calculate the density of the material for a vibrating string

    Here is the question that is is given to me Part a: Part b: I have given this a go and was wondering if my answer seems reasonable. I had worked out that the mass per unit length (mu) is also the density * cross sectional area of wire Thanks!
  24. RicoY65

    What is the frequency of the second harmonic on the A-string in guitar tuning?

    We’re tuning a guitar using harmonics, and we produce, on our properly tuned E-string, a frequency of 329.6 Hz when we pluck the first harmonic. The second harmonic, on the A-string, is noticeably higher, producing a beat frequency of 1.5 Hz. What is the frequency produced by the harmonic on the...
  25. DEvens

    Representing Logical Combinations in Analysis Programs

    I have an analysis program. (It's MCNP if it makes any difference.) Part of the input is to specify the surfaces of a cell in a string of "this side of surface x" and "that side of surface y" entries. It looks a little something like this. ((a b):(c -d)):(f -g)) So the : means "or" and...
  26. V

    Comp Sci Return the number of times a word appears in a string

    def count_code(str): count = 0 for c in range(len(str)-1): if str[c] == 'c' and str[c+1] == 'o' and str[c+2] == 'd' and str[c+3] == 'e': count+=1 return count Here is my code so far, I did use some test results with print...
  27. S

    A Can Cosmic Inflation and String Theory change fundamental laws?

    Is there any version of string theory or cosmological inflation that allows the most fundamental laws and constants change between universes? String Theory and Cosmological Inflation are two theories or models that allow multiple universes to exist. Laws and constants of physics could change...
  28. G

    To find the amplitude of a mass on an elastic string

    Could I please ask for help with the following: It's the final part I am having problems with. So at this point we know we have SHM of amplitude (5/4)L Now, using x = a cos(nt) ----- where we now know that n = sqrt(4g/L) we can find the time at which x has any value. So for exmaple, when...
  29. Srinath

    Timoshenko Beam Theory (Violin String Shape Functions)

    Homework Statement:: Violin String Shape Functions Homework Equations:: Violin String Shape Functions Hello, Is anyone working on violin string shape functions(Timoshenko Beam Theory)? It would be really helpful to my research if we share our knowledge on this topic. Thank you
  30. A

    How Do You Calculate the Tension of a Cello String?

    wavelength of string= 2*L wavelength of string=2*0.70m= 1.4m velocity of string= frequency * wavelength velocity of string= 220Hz * 1.4m= 308 m/s tension= (308m/s)^2 * 0.00196 kg/m =186N Is the tension correct?
  31. G

    MHB Arithmetic string equal to the geometric string, count x

    Let x1, ..., x25 be such positive integers that x1⋅x2⋅ ... ⋅x25 = x1 + x2 + ... + x25. What is the maximum possible value of the largest of numbers x1, x2, ..., x25?
  32. G

    To find the equilibrium position of a mass attached to an elastic string

    Hi, can anyone see if I have made an error in answering this simple question, my answer is not the one given in the textbook. Here's my diagram of the system in equilibrium. So the mass has dropped a distance x below the midpoint of PQ: So the forces balance as: T1 = g + T2 So, using...
  33. B

    Length of a string over a 2 pulley system

    Hello all, I am working on a lab report for physics, and am a bit stuck on one aspect. The basic layout of the pulley system is attached. (This is a diagram I made, so if there are any inaccuracies in this one either, I am happy to fix it. So, I mostly understand the lab. My TA said, though...
  34. G

    Travel time of a particle suspended from an elastic string

    Hi, Can anyone please help me with the following: I have found the velocity of projection, no problem, it is v = 2*sqrt(10) Also, in obtaining this value, I have also found the extension in the string when in equilibrium, it is x = 2 Now on to the time of flight. The given answer is: t =...
  35. M

    Exploring the Relationship Between String Tension & Audio Output Amplitude

    I am working on a guitar/piano synthesizer for my own interest. When a string is plucked or struck, tension increases causing a slight pitch bend and change in the inharmonicity. This change then settles as the note quiets down. Thus it is important to model how the tension rises above baseline...
  36. P

    Whats the tension T' in string 1 if tension of highlighted string is T

  37. A

    Find the Total Energy of the String

    Steps that I've taken: First, compute the derivative of the psi-function with respect to time and then take the square of the result Second, input the result into the KE integration formula. All that is left is to find the integrand, however this is where calculations became really "messy". It...
  38. J

    Addition of Harmonics in a string wave

    In basic optics, we are given the general solution of the wave equation (massless string of length L) as a linear combination of normal modes, that need to have some of the permitted frequencies due to boundary conditions. In laboratory, we observed that phenomenon. We generated a wave in a...
  39. dRic2

    Are harmonics "real" in a vibrating string?

    This question reminds me of the interpretation of the "wave packet" in QM for a free particle moving freely in the whole space; but in QM it is obvious that plane waves can't be of physical meaning. Now consider a guitar string (fixed at both ends) and suppose the solution to the wave equation...
  40. M

    MHB TM: Is the given string of the form uu?

    Hey! :o I am looking at the following exercise: Construct a composite Turing machine $M$ that has a word $w$ over the alphabet $A = \{a, b\}$ tests to see if it's made up of two equal parts, that is, if $w = uu$ with $u \in {a, b}^+$. In this case, at the end of the method a $1$ has to be...
  41. Asterast

    Tension in the string while it descends

    so I took string below point A and Block as a system. Taking mass of string below point A as m and mass of block M. Taking downward direction as X axis. I get Mg+mg-T, Taking T as tension by upward part of string. Now the question says about block descending with acceleration a. so again forces...
  42. S

    Tension in a String: Solve for Unknown Lengths - 98.6N

    I know that the answer has to be 98.6N. So I know that Fy=0 so that 2*T*sin(theta) = 147.25. Then I was think to take the torque of the left wheel but I can't find the lever arm of the tension force. I also know that u can solve the question by saying that the 2 sides of unknown length are 1.5 m...
  43. Old-Alien

    A string attached to a fixed wall and a mass on a spring

    Hi all. Multiple part problem that I'm really stuck on. I'll attach a file. At first I had attempted the whole problem with the idea that fixed wall was a fixed point, and that the mass on a spring was a "free" point. But I learned later that the mass can't be treated like a "free" point since...
  44. J

    I Wave damping on a stretched string

    Is there a simple model I can use to describe the damping of a wave on a string? Is c = 2*mu*sqrt(T/mu) where mu is damping coefficient, mu is linear density and T is tension a valid option? I replaced k and m with T and mu from the simple equation found here. What I am interested in showing is...
  45. P

    A Real image of a sawtooth standing wave in a musical string?

    Hi there I am teaching resonance and standing waves in stringed instruments at the moment at high school. The theory states that a number of standing waves simultaneously (harmonics) exist in a naturally vibrating musical string, but with varying amplitudes, the 1 st harmonic being loudest...
  46. Kaushik

    B How Does a Man Accelerate While Climbing a Rope?

    A man tries to climb up a rope with acceleration, ## a ##. What does he actually do to climb up? My Interpretation Let the man pull the rope at point A. So the Point A will pull the man with Tension, ## T ##. But at the same time the man is holding the rope, so there will be some normal...
  47. novera

    Seemingly simple Physics 2 wave question (third harmonic frequency)

    I cannot find the correct answer anywhere online and the answer I keep getting is 5.4 (incorrect) Please show me the process to get to the answer! Thank you
  48. filip97

    A Spin Matrices & Higher Spin Tensors: Find Answers Here

    i can't find on internet why higher spin tensors are totally simetric. know this anyone ? I think that is connected to spin matrices.
  49. A

    A What topics in Quantum Gravity don't require QFT or string theory?

    Full quantization of gravity is a big issue, but that's not what I'm asking here. I'm asking about quantum effects that involve any form of gravitation (Newtonian or GR) but that don't require a full quantization of GR or anything like that. Things like gravitational neutron interference or the...
  50. b1llso

    Find the EMF generated by a guitar string in the pickup coils

    I tried using the general EMF equation but don't know how to apply it with the equation from the problem
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