A theory is presented on dose calculations in inhomogeneous media that takes advantage of fast Fourier transform (FFT) convolution for practical 3-D treatment planning using photon beams. We derived a new correction dose formula which corrects the dose deposited by the Compton rst scattered photons due to the presence of inhomogeneities. We justiied theoretically why the convolution primary dos...

Using reflection spectroscopy of optically pumped sodium vapor, we have performed what is to our knowledge the first direct measurement of the spatially inhomogeneous spin polarization near a glass surface. On the basis of a theoretical description of the reflection at an inhomogeneous, anisotropic medium, we deduce the magnitude of the small residual magnetization at the surface from an analys...

Formulas are derived for solutions of many-body wave scattering problems by small particles in the case of acoustically soft, hard, and impedance particles embedded in an inhomogeneous medium. The case of transmission (interface) boundary conditions is also studied in detail. The limiting case is considered, when the size a of small particles tends to zero while their number tends to infinity a...

In an inverse scattering problem, the fields in the inhomogeneous wave equation are known, and it is desired to solve for the source term. N. N. Bojarski has recently derived an Exact Inverse Scattering Theory for such "inverse source" problems. The problem of determining the generalized refractive index (i.e., the complex permeability and dielectric constant for an electromagnetic problem, or ...

An effective-medium approach is used to derive a set of coupled-mode equations describing quadratic parametric interactions in a one-dimensional inhomogeneous medium of finite length. The solutions for both copropagating and counterpropagating interactions are used to study the quantum-mechanical process of spontaneous parametric down-conversion (SPDC). An example is studied in which the inhomo...

Although the exact details are disputed, it is well established that propagating waves of increased intracellular free Ca2+ concentration arise from a positive feedback or autocatalytic mechanism whereby Ca2+ stimulates its own release. Most previous modeling of the propagation of Ca2+ waves has assumed that the sites of autocatalytic Ca2+ release, the activation sites, are homogeneously distri...

für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution 4.0 International License. Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namen...

The intergalactic medium (IGM) prior to the epoch of reionization consists mostly of neutral hydrogen gas. Lyman-α (Lyα) photons produced by early stars resonantly scatter off hydrogen atoms, causing energy exchange between the radiation field and the gas. This interaction results in moderate heating of the gas due to the recoil of the atoms upon scattering, which is of great interest for futur...

We consider the initial value problem for the filtration equation in an inhomogeneous medium ρ(x)ut = ∆u, m > 1. The equation is posed in the whole space R, n ≥ 2, for 0 < t < ∞ ; ρ(x) is a positive and bounded function with a certain behaviour at infinity. We take initial data u(x, 0) = u0(x) ≥ 0, and prove that this problem is well-posed in the class of solutions with finite “energy”, that is...