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. throneoo

    Energy in a long inextensible string

    Homework Statement Find the maximum kinetic energy and total energy of the system if a string(with uniform linear density) of length L and mass M is oscillating as a standing wave with two fixed ends in its fundamental frequency f with amplitude 2A Homework Equations let x=0 and x=L be the...
  2. J

    Solving the Tension in a String Attached to a 10 kg Block

    Homework Statement A string is attached to a 10 kg block that lies on a horizontal surface. If the string is pulled horizontally with a force of 50 N, friction acting against it is 30 N. What is the tension in the string? Homework Equations F = ma The Attempt at a Solution Would it be 50 N...
  3. M

    MATLAB [Matlab] How to use inputdlg string variable in text file?

    I am trying to display the input that I enter into the dialog box from "inputdlg" function into a text file. This is what I've so far: prompt={['What is your name?']}; title = 'Name Machine'; answer = inputdlg(prompt, title); name = answer{1}; fileID = fopen('NameMachineFive.txt', 'w')...
  4. J

    What Determines the Note of a Guitar String When Plucked?

    When you pluck a guitar string it resonates at its fundamental frequency plus some of the overtones. My question is, what exactly determines the note (i.e. A,C, E etc) for, say, a guitar? For example, if note A is 440Hz then what is it that is at 440Hz because some instruments have lots of...
  5. moriheru

    Learn Bosonic String Theory Before New Year's Eve!

    Greetings, I am intending on learning bosonic string theory in self study before new years eve and I nead a ruff and short introduction on the basics and the idea of gauge theory. The introducton is preferably in PDF form, yet books are fine to.
  6. J

    Friction and tension in a string

    Homework Statement Mass m1 = 5.00kg is tied to the wall with a horizontal piece of string and is at rest onto of mass m2 = 10.00kg. A horizontal force F= 50.0N is applied to m2. The static coefficient of friction between all surfaces is μs = .350 and the kinetic coefficient of friction is μk =...
  7. PhysicsKid0123

    Infinite acceleration on a string?

    I'm trying to figure out what it says in my book. Here is the link of the picture. http://i941.photobucket.com/albums/...oads/7D0D3CE4-A11E-4F0F-A2A5-836D03945AE5.jpg Could someone explain the part where it says "Otherwise, there would be a net tension force acting on the sections, and they...
  8. moriheru

    Graviton exchange for two freely propagating particle:solution String theory?

    Consider the feynman diagramms for two freely propagating particles...Correction from one graviton exchange. Correction from two graviton exchange.The problem at hand is the divergence (of the math) at arbitary energys and each additional graviton exchange. So there are several resoultions and...
  9. moriheru

    Introductory Books for Research in Bosonic String Theory

    I am looking for introductiory books on gauge theory and conformalfield theory and polyakov integrals for research in Bosonic string theory. Any other material recommendations for String theory that are necessary for bosonic string theory or heterotic string theory are definelty apreciated. To...
  10. F

    Tension in String between two blocks

    Homework Statement Block 1, of mass m_1 =2.6kg and block 2 of mass m_2=1.4kg are connected by a massless string. Block 2 then experiences a force F=18N acting in the postivive x direction and at an angle of \theta = 38° . The coefficiant of kinetic friction between the floor and both of the...
  11. A

    Please help, conceptual motion of a transverse wave on a string question

    I am losing my mind over this, it seems the longer i think about it the further i get from a definitive answer. It started with me trying to understand the variables the would result in a standing wave, ie: what needs to occur, why, and how it occurs. At first i was confused because it seemed...
  12. L

    Solving for Acceleration of Mass on Cylinder w/ Frictionless String

    Homework Statement [/B] A solid cylinder of mass m and radius r lies flat on frictionless horizontal table, with a massless string running halfway around it, as shown in Fig. 8.50. A mass also of mass m is attached to one end of the string, and you pull on the other end with a force T. The...
  13. B3NR4Y

    Two Carts attached to a string

    Homework Statement Two 0.400-kg carts are 100 mm apart on a low-friction track. You push one of the carts with a constant force of 2.0N directed so that the cart you push moves away from the other cart. Determine the acceleration of the center of mass of the two-cart system when the carts are...
  14. D

    Waves on a String: Exploring Transverse Force

    In my wave course at the moment we are looking at waves on a string and their applications. At one point we consider the transverse force at a particular point on the string due to a uniform tension throughout a string. Something about this has confused me, the force isn't at all in the form I...
  15. T

    Calculating Oscillation Frequency and Max Acceleration of a String

    For the first part of the equation, I worked out k constant of a string which extended 12.6cm when a mass of 300g was suspended from it using the equation F = kx where F is the force applied and x its extension. So mg = xk, 300 x 9,81 = 0.126k, the answer was 23357N/m (23kN/m). The question...
  16. S

    Exploring Polyakov's Action: Diffeomorphism Symmetry?

    The Polyakov action, S=\frac{1}{4\pi\alpha^\prime}\int d^2\sigma\sqrt{-h}h^{\alpha\beta}G_{ij}(X)\partial_\alpha X^i\partial_\beta X^j has the local symmetries, diffeomorphism on world sheet and the Weyl invariance. But is diffeomorphism on the target space also a symmetry? The target space...
  17. A

    Simple Harmonic Motion Guitar String Question

    Homework Statement Question: "The midpoint of a guitar string oscillates with an amplitude of 2.24mm with a frequency of 400Hz. Calculate: i) The maximum speed at this point ii) The maximum acceleration of the string at this point" Homework Equations Suitable formulas: x=Asin(2*pi*f*t) ...
  18. B

    Why are standing waves on a guitar string sinusoidal?

    Ok I understand the idea that a standing wave can be represented as the sum of two traveling waves going in opposite directions with same stuff but what I don't understand is why the waves on a guitar string are sinusoidal. I mean I know looking at them, they look sinusoidal but could they be...
  19. P

    Does string theory need to start with our observable universe?

    This will, no doubt, sound like a silly question but I am just getting my feet wet in string theory. It seems from what I know so far, that string theory is very far removed from our observable universe. What I mean by that statement is that it seems we just say "well, maybe our universe is a...
  20. T

    Analyzing a Simple Pendulum: Length, Displacement, Velocity, and Restoring Force

    Homework Statement A mass,m, hangs from a string and swings with a frequency of 0.8 Hz with a maximum displacement of 0.1 rad. The equation of motion is given by x=Acos(ωt). A) What is the length of the string? B) What is the maximum displacement of the mass in meters? C) What is the velocity...
  21. T

    Speed of wave on guitar string

    Homework Statement A 65-cm guitar string is fixed at both ends. In the frequency range between 1.0 and 2.0 kHz, the string is found to resonate only at frequencies 1.2, 1.5, and 1.8kHz . What is the speed of traveling waves on this string? Homework Equations f = v/2l The Attempt at a...
  22. I

    C/C++ C++: Replacing Characters in A String

    Replace any space ' ' by '_' in 2-character string passCode. Sample program: #include #include #include using namespace std; int main() { string passCode; passCode = "1 "; <student code> cout << passCode << endl; return 0; } I'm super lost on this. I could...
  23. I

    C/C++ C++: Determining If a String Contains A Numeric Digit

    Set hadDigit to true if the 3-character passCode contains a digit. Sample program: #include #include #include using namespace std; int main() { bool hasDigit = false; string passCode; int valid = 0; passCode = "abc"; <student code> if (hasDigit) { cout << "Has a...
  24. I

    C/C++ Detecting First Letter Match in C++ String with Substr Function

    Write an expression to detect that the first character of userInput matches firstLetter. Sample program: #include <iostream> #include <string> using namespace std; int main() { string userInput; char firstLetter = '-'; userInput = "banana"; firstLetter = 'b'; if (<STUDENT...
  25. I

    C/C++ C++ String Access Ops: Assign Size of UserInput

    Assign the size of userInput to stringSize. Ex: if userInput = "Hello", output is: Size of userInput: 5Sample program: #include <iostream> #include <string> using namespace std; int main() { string userInput; int stringSize = 0; userInput = "Hello"; <STUDENT CODE> cout <<...
  26. D

    MHB Wave equation of string under tension with a mass at x(a)

    We have a string of length \(\ell\) with fixed end points. At \(x(a)\), we have a mass. We can break the string up into two sections \(a + b = \ell\); that is, a is the distance up to the mass and b afterwards. The string is under tension \(T\). My question is why is the DE then \[...
  27. PsychonautQQ

    String with mass pulling block up frictionless ramp

    Homework Statement A block of mass M has a string of mass m attached to it. A force F is applied to the string and it pulls the block up a frictionless plane that is inclined at an angle theta. Find the force that the string exerts on the block Homework Equations F=ma The Attempt at a...
  28. I

    C/C++ Two question on string access ops c++

    Assign the size of userInput to stringSize. Ex: if userInput = "Hello", output is: Size of userInput: 5 Sample program: #include <iostream> #include <string> using namespace std; int main() { string userInput; int stringSize = 0; userInput = "Hello"; <STUDENT CODE> cout <<...
  29. I

    C/C++ C++ String Compare: Alphabetize Strings

    Print the two strings in alphabetical order. Assume the strings are lowercase. End with newline. Sample output: capes rabbits Sample program: #include <iostream> #include <string> using namespace std; int main() { string firstString; string secondString; firstString = "rabbits"...
  30. D

    Natural position of a string wrapping around a cone

    I've had a problem I encountered at work some time ago and took a personal interest in. I never did end up solving it, but I've recently looked at it again. It goes like this: You have an axisymmetric part, such as a cone, and it's positioned such that its central axis is coincident and...
  31. C

    High school string theory project

    Hi, so I'm new to this forum and wanted to ask for some advice. I REALLY am interest in string theory and I've read around the topic a lot without actually learning about it. In my school we can do an independent study project or ISP. When students do ISPs they have to have a project that can be...
  32. S

    Two Blocks attached by a string, on an incline

    Homework Statement In the diagram mA is equal to 3.00 kg and mB is equal to 1.07 kg. The angle of the inclined plane is 38.0° (a) Find Acceleration: 6.03 m/s^2 (got this part) (b) Find the tension Tb in the connecting string: Not sure Homework Equations (a) a = (F/mA + mB) (b) t =...
  33. S

    Is the Big Bang replaced with a Big Bounce in String-Inspired Cosmology?

    We have made a third film in our "Before the Big Bang" series for youtube. Our first centred around an interview with Abhay Ashtekar and focused on LQC Our second Sir Roger Pernose on CCC This fetaures an interview with Gabrielle Veneziano (founder of string theory), Ali Nayeri ( who works...
  34. L

    How do string waves pass through each other without interfereing?

    From what I have learned so far a wave propogates on a string by having the point on the string (that is closest to the wave and in the direction the wave is moving) move upwards or downwards depending on the wave and this point moving due to tension causes the next to move simillarly and thus...
  35. R

    Determining the ratio of wave amplitudes along a string

    Homework Statement A point mass M is concentrated at a point on a string of characteristic impedance ρc. A transverse wave of frequency ω moves in the positive x-direction and is partially reflected and transmitted at the mass. The boundary conditions are that the string displacements just to...
  36. James889

    What are the issues with this code for reversing a string in memory?

    Hi, I'm trying to write a simple program for reversing a string stored in memory. This is what I've come up with. For some reason this code coredumps, so something is wrong. any ideas ? #include <stdio.h> #include <string.h> #include <stdlib.h> char *reverse(char *buf,unsigned...
  37. J

    Connection between particles a field in string theory

    Im a trying to understand how the string entity relates to its underlying field. Is the field a brane and the string the partice?
  38. C

    Java Trying a String exercise in JAva

    I am trying to capitalize the first letter of every word in a sentence. Example. "hey what's up" would be "Hey What's Up". here is my code but nothing is changing the sentence. I thought everything was right. public static String cap(String aString) { String[] sentence = aString.split("...
  39. D

    QFT & String Theory: "Particle First" vs "Field First

    As Steven Weinberg put it, "the idea of quantum field theory is that quantum fields are the basic ingredients of the universe, and particles are just bundles of energy and momentum of the fields." At least, this is one way to look at QFT. The other approach is to imagine that these particles are...
  40. D

    Forces on a string applied perpendicular / tangent direction

    Hello guys, I've had the following discussion at work: We are currently using a suture with a nylon thread on a tissue, when the thread of the suture is tightened in a force equal to if we've put a 500 gram weight on both ends of the suture line (meaning both end are tied together to the...
  41. Jackson Lee

    Could transverse wave on a string could be used to produce sound?

    I feel curious about why we pay so much attention on standing waves on the string. Doesn't transverse wave on the string can't be used to produce sound?
  42. F

    Is there really no way to test string theory?

    Here's an idea that I came up with. I've heard over and over again that there is no test yet available to confirm string theory. So what I say is... What if you could derive some fundamental physics equation from string theory principles? Then wouldn't that be a test so to speak...
  43. J

    Find the Smallest Possible Tension in a Massless String Supporting a Disk

    A disk of mass M and radius R is held up by a massless string. (The two ends of the string are connected to a ceiling and the disk rests on the bottom of the string.) The coefficient of friction between the disk is μ. What is the smallest possible tension in the string at its lowest point...
  44. Jackson Lee

    Does plucking one point on the string really can cause standing wave?

    I was teaching myself standing wave's chapter. It is said in the book that when plucking in the center of the string, it will cause two traveling waves of different directions, one left, one right. Then both of them will reach ends of string and invert back. Before they encounter at the center...
  45. B

    Calculating Waves on a String: Answer Justification and Confusion Dispelled"

    Hi all, I cannot seem to find a way to justify my book's answer to this problem: One end of a string is shaken each second sending a wave with an amplitude of 10cm toward the other end. The string is 5m long and wavelength of each wave is 50cm. How many waves reach the other end of the string...
  46. S

    Low curvature effective action in string theory

    String effective action: S=-\frac{1}{2\lambda_{\text{s}}^{d-1}}\int d^{d+1}x\sqrt{|g|}e^{-\phi}\left[R+(\nabla\phi)^2+2\lambda_{\text{s}}^{d-1}V(\phi)-\frac{1}{12}H^2\right]+S_m where H^2=H_{\mu\nu\alpha}H^{\mu\nu\alpha}\\ H_{\mu\nu\alpha}=\partial_\mu B_{\nu\alpha}+\partial_\nu...
  47. W

    String Theory Vs Loop Quantum Gravity

    This is a question currently pondered by many Quantum physicists and theoretical physicists. I was just wondering how many of you prefer ST(string theory) as opposed to LQG(loop quantum gravity.) Please provide points and reasons regarding your answer. I will provide an opinion when a few...
  48. T

    How to Express the Curve of a String Hung Between Two Columns

    1. Imagine two columns between which is hung a string. The hung string may be expressed graphically and mathematically as a parabola whose nature is exponential. If these columns are moved closer together or farther apart, the hung string becomes more loose or taut according to a trigonometric...
  49. C

    Exploring the New Geometry of String/M-Theory

    I'm watching a lecture by Edward Witten here: In it, he mentions that String/M-theory seems to be hinting toward a new kind of geometry where you don't talk about space/time points, but the interactions between quantum world sheets (around 37:00 minute mark.) Does this new geometry have...
  50. evinda

    MHB Cost of the conversion of a string to an other string

    Hello! (Wave) We are given $2$ strings $A=[1 \dots m]$ and $B[1 \dots n]$ and the following $3$ operations are allowed: Insert a charachter,with cost $c_i$ Delete a character,with cost $c_d$ Replace a character,with cost $c_r$ We are looking for the optimal sequence of...
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