Conditions Definition and 978 Threads

This new paper in Nature Genetics: http://www.nature.com/ng/journal/v37/n8/abs/ng1608.html suggests that considerable variance in lifetimes of C. Elegans with controled, identical genomes, is caused by an essentially random variable; the first encounter with a certain chemical in its...

I have to write a short essay answering this question (1st year university level). I am finding it very hard to get any decent info on the net at all. If someone could help me out with this I would be very appreciative. Thanks. Regards Graeme

Let's have hermitian matrix A. Then these three conditions are equivalent: 1) A is positively definite \forall x \in \mathbb{C}^{n} \ {0} : x^{H}Ax > 0 2) All eigenvalues of A are positive 3) There exists regular matrix U such that A = U^{H}U Proof: 2) \Rightarrow 3)...

Hi there, i have a question about the energy-momentum tensor T of a perfect fluid, en the relations between pressure en density. I've read something about the Dominant Energy condition, which states that the contraction between T and 2 null- or timelike vectors is always positive. This I...

DEC is related to superluminal acoustic modes. I can not understand. Help me. Thanks.

Under what conditions will quantum effects become important for gravity?

The equation of motion of an undamped harmonic oscillator with driving force F=F_ocos(\omega*t) is x(t) = Acos(\omega_0*t) + Bsin(\omega_0*t) + \frac{F_0}{m}\frac{cos(\omega*t)}{\omega_0^2-\omega^2} I am to determine the initial conditions such that the undamped oscillator begins steady...

I have had a few people say, turn on a light when your on the computer, or your going to ruin your eyes. I have spent the last 10 years behind a computer screen never with a light on. My eyes are perfectly fine. When I went for drivers license i for 20/20 and the smallest font size was...

I have been taught that the equation Ax^2 + Cy^2 +Dx + Ey +F = 0 represents a general form of conics. Then the conditions of the coefficients in the equation could identify which type of conics the equation represents... Circle: A=C Ellipse: A does not=C and AC>0 Hyperbola: AC<0 and...

I heard that there are so many conditions neccesary for us who are living on the Earth. Surely somebody must have collected them before. But I have a suggestion. What if PF people collect them once again in this thread? Anybody who knows some neccesary conditions for our existence on Earth...

Hello guys, I have a question regarding mathematical logic that I'm stuck on. Here it is: T = { (5,9), (4,9), (5,7), (6,5), (5,5), (6,3), (7,1), (6,1), (5,1), (4,1), (3,1), (2,1), (1,1), (0,1) } F = { (5,4), (6,8 ), (2,11), (4,13), (8,1), (1,0) } 1) Make a simple open statement...

I need to know how different boundary conditions on the DE representing a string under a force can be physically implemented. For example, if you need y(0)= 0, just tie the string to y=0 at that end. If you need y'(0)=0, attatch it so that it can freely slide up and down a pole at x=0. But...

As the thread title says: What's the difference between initial conditions and boundary conditions? Thanks in advance for helpful replies. :)

I need to find all the separated solns of x^2 \frac{\partial^2 u}{\partial x^2} + x\frac{\partial u}{\partial x} + \frac{\partial^2 u}{\partial y^2} = 0 in the strip {(x,y) : 0 < y < a, -\infty < x < \infty } the separated solns must also satisfy u = 0 on both the edges, that is, on...

I am familiar with the normalization \int\left|\Psi\right|^{2}dx=1 Because we want to normalize the probability to 1. However if a state vector isn't in the x basis and is just a general vector in Hilbert space, we can take the normalization condition to be: <\Psi|\Psi>=1...

Here's my problem: For each kW of power input to an icemaker at steady state, determine the maximum rate that ice can be produced in kg/h, from liquid water at 0 C. Assume that 333 kJ/kg of energy must be removed by heat transfer to freeze water at 0 C, and that the surroundings are at 20 C...

I'm having trouble with the meaning of the boundary condition in the derivation of fresnels quations, namely that the component of E tangental to the surface is continuous across the boundary. My trouble is, what physically does this corresspond to. Is it something to do with the divergence...

Ok, I am told in a complex analysis book that the gradient squared of u is equal to the gradient squared of v which is equal to 0. We know the derivate of w exists, and w(z)=u(x,y) + iv(x,y) Thus the Cauchy Riemann conditions must hold. (When I use d assume that it refers to a partial...

That is the title of the famous Schrödinger's book (1944), which inspired to scientists as Crick. Now, after the great discoveries in Biology, mainly in Molecular Genetics, the question remains. We know essential aspects of living organisms: need of some type of informative...

"This is supposed to be an all-volunteer military," said Jessica Salamon, who has been to therapy and has seen her dream of starting a family deferred. "They're not volunteering when they're told they can't leave." http://www.washingtonpost.com/wp-dyn/articles/A10961-2004Jun2.html Soldiers...

Hello there, I am glad that I found this forum. Because I have a little bit trouble with theoretical physics. The problem is the Green function in theoretical electrodynamic. I try to understand the difference between the Dirichlet Condition and the Neumann Condition. I understand...

Under what conditions is the renunciation of one's country justified?

I was doing a question which involved using euler's method to numerically integrate the equation dy/dt=2ty^2 in the interval [0,1], with h=0.2 but no initial conditions were given. How do I find them. I know it's something simple but I can't get it. Thanks

I'm so confused about what to do for this problem... I know that I need to find K for the given conditions but I'm not quite sure how. Any help would be greatly appreciated For each of the following sets of conditions, determine if the system is at equilibrium or not. For those not at...

I have 3 probs I'm working on, not really sure how to go about these... 1) A gas, while expanding under isobaric conditions, does 611 J of work. The pressure of the gas is 1.70 x 10^5 Pa, and its initial volume is 1.30 x 10^-3 m^3. What is the final volume of the gas? I'm assuming I would...

a function with certain conditions on derivatives at 0-generating functions i don't know how to do superscripts, so let's say [f,n](x) is the nth derivative of f at x. let A be the set of infinitely differentiable functions from I to R where I is some possibly infinite open interval...

1)Find equations of both lines through point (2,-3) that are tangent to the parabola y=x^2+x. 2)The normal line to a curve c at a point Pis, by defininiton, the line that passes through p and is perpindicular to the tangent line c at P. Where does the normal line to the parabola y=x^2-x...

This is a homework question so please do not just tell me the answer, but please point me in the right direction. A dipole layer, D(y,z), exists on the plane x=0. Find the boundary conditions (discontinuities, if any) for [phi](x,y,z), E_x(x,y,z), E_y(x,y,z), and E_z(x,y,z) across the...